CommandParameter是否始终为null，或者您是否只在第一次执行时检查它？
在这种情况下，声明属性的顺序似乎很重要，因为设置Command属性会导致CanExecute在CommandParameter设置之前立即触发。
尝试将CommandParameter属性移到Command属性之前：

<Button Content="Edit" HorizontalAlignment="Right" Height="20"  Width="80"
 CommandParameter="{Binding PersonModelProp}" 
 Command="{Binding EditPersonCommand}" />

另请参见here和here。

编辑

若要确保正确引发事件，应在PersonModelProp值更改时引发CanExecuteChanged事件。
命令：

public class EditPersonCommand : ICommand
{
  public bool CanExecute(object parameter)
  {
     PersonModel p = parameter as PersonModel;
     return p != null && p.Age > 0;
  }

  public event EventHandler CanExecuteChanged;

  public void Execute(object parameter) 
  {
      //command implementation
  }

  public void RaiseCanExecuteChanged()
  {
      var handler = CanExecuteChanged;
      if(handler != null)
      {
          handler(this, EventArgs.Empty);
      }
  }
}

视图模型：

public class PersonViewModel : ViewModelBase
{
  private PersonModel _PersonModel;
  private EditPersonCommand _EditPersonCommand;

  ///<remarks>
  /// must use the parameterless constructor to satisfy <Window.Resources>
  ///</remarks>
  public PersonViewModel()
     : this(new PersonModel())
  {
      _EditPersonCommand = new EditPersonCommand();
  }

  public PersonViewModel(PersonModel personModel)
  {
     _PersonModel = personModel;
  }

  public ICommand EditPersonCommand
  {
     get
     {
         return _EditPersonCommand;
     }
  }

  public PersonModel PersonModelProp
  {
      get
      {
         return _PersonModel;
      }
      set
      {
         _PersonModel = value;
         OnPropertyChanged("PersonModelProp");
         EditPersonCommand.RaiseCanExecuteChanged();
      }
    }
}

答案有两点：
首先，正如@akton提到的，你只能绑定到 public properties。它不一定是DependencyProperty**。
第二，我花了一些托姆才弄明白，您必须在Command属性之前设置CommandParameter的绑定。即

<Button Content="Edit" HorizontalAlignment="Right" Height="20"  Width="80"
        CommandParameter="{Binding PersonModelProp}"
        Command="{Binding EditPersonCommand}" />

希望这有帮助：）

_PersonModel是私有的，因此无法访问。创建一个公开它的公共属性并绑定到CommandParameter中的公共属性。请记住，将属性设置为依赖属性（技术上不是必需的，但它有帮助），ViewModel应该实现INotifyProperty changed并触发PropertyChanged事件，以便更新绑定。

我想你的EditPersonCommand有问题（它没有被激活）。我用relayCommand检查它，它工作了!
这就是代码：
视图模型：

public class PersonViewModel : ViewModelBase
    {
        private PersonModel _PersonModel;
        private ICommand _EditPersonCommand;

        ///<remarks>
        /// must use the parameterless constructor to satisfy <Window.Resources>
        ///</remarks>
        public PersonViewModel()
            : this(new PersonModel())
        {

        }

        public PersonViewModel(PersonModel personModel)
        {
            PersonModelProp = personModel;
        }

        public ICommand EditPersonCommand
        {
            get
            {
                if (_EditPersonCommand == null)
                {
                    _EditPersonCommand = new RelayCommand(ExecuteEditPerson,CanExecuteEditPerson);
                }
                return _EditPersonCommand;
            }
        }

        private bool CanExecuteEditPerson(object parameter)
        {
            PersonModel p = parameter as PersonModel;

            return (p != null) && (p.Age > 0);
        }

        private void ExecuteEditPerson(object o)
        {

        }

        public PersonModel PersonModelProp
        {
            get
            {
                return _PersonModel;
            }
            set
            {
                _PersonModel = value;
                NotifyPropertyChanged("PersonModelProp");
            }
        }

    }

而这个RelayCommand（Fire events ok!）

public class RelayCommand : ICommand
        {
            #region Constants and Fields

            private readonly Predicate<object> canExecute;

            private readonly Action<object> execute;

            #endregion

            #region Constructors and Destructors

            public RelayCommand(Action<object> execute)
                : this(execute, null)
            {
            }

            public RelayCommand(Action<object> execute, Predicate<object> canExecute)
            {
                if (execute == null)
                {
                    throw new ArgumentNullException("execute");
                }

                this.execute = execute;
                this.canExecute = canExecute;
            }

            #endregion

            #region Events

            public event EventHandler CanExecuteChanged
            {
                add
                {
                    CommandManager.RequerySuggested += value;
                }

                remove
                {
                    CommandManager.RequerySuggested -= value;
                }
            }

            #endregion

            #region Implemented Interfaces

            #region ICommand

            [DebuggerStepThrough]
            public bool CanExecute(object parameter)
            {
                return this.canExecute == null || this.canExecute(parameter);
            }

            public void Execute(object parameter)
            {
                this.execute(parameter);
            }

            #endregion

            #endregion
        }

Xmal：

<Button Content="Edit" HorizontalAlignment="Right" Height="20"  Width="80"
 CommandParameter="{Binding PersonModelProp}" 
 Command="{Binding EditPersonCommand}" />

命令参数必须允许null

[RelayCommand]
private void ClickForm(int? id)
{
    MessageBox.Show(id.ToString());
}