How to apply group policy to security group?

It's not possible to apply a group policy to a security group . However, you can change the permissions on group policy so that only certain users/groups have read and apply privileges.

Step 1:

Select the Group Policy Object in the Group Policy Management Console (GPMC). Click on the Delegation tab and then click on the Advanced button.

Step 2:

Click on the Add button and select the security group that you wish to apply to . Then select the group (e.g. “Accounting Users”) and scroll the permission list down to the “Apply group policy” option and then select the Allow permission.

This Group Policy now applies to only users or computers that are a member of the Accounting Users security group. However you still need to remember that the user and/or computer should be part of the site/domain/OU to which this Group Policy Object is linked.