What do you mean by "system password character".
Do you mean that when someone types data into the column it must be hidden and look like "*******"?
If so you will need to make a custom DataGridColumnStyle class
Your class will have to inherit from either the DataGridColumnStyle class or one of the existing classes like DataGridTextBox class.
There are examples of custom DataGridColumnStyles in codeproject
DataGrid ColumnStyle as LinkLabel.
And
MSDN articles on how to do that.