i am trying to develop my theme and problem about add slider in header so plz tell me how to add image slider in theme
Well you could use a plugin to add to your header.php file. or you could create a slider and place the code in the header.php file. If you are making a custom theme you should find a slider that you like and incorporate into you theme. You should create a shortcode with a slider and then insert into your content as well.
To answer your question more directly.. if you want to add anything in to your theme's header, you need to edit the header.php file.