Will anyone help me how to add custom fields in registration form, user name, password, email is not enough for my project, i needed more fields for that.. If anyone have an idea please let me know it..
Joomla has a built-in User - Profile plugin which you can enable. That will add and let you control many additional fields that you can add to the registration form.
Beyond that, you'd need to use a 3rd party profile extension, of which there are many, to add profile management features to your site.