Operation Scenario
If your business no longer needs one or multiple security groups, you can delete them. After you delete a security group, all security group rules in the group will also be deleted.
Prerequisites
The security group to be deleted is not associated with any instances. If it is associated with instances, remove them from the security group first. Otherwise, the security group cannot be deleted. For details about the operation, see Removing from a Security Group. Steps
2. On the security group management page, choose Region, and locate the row of the security group to be deleted.
3. In the operation column, click More > Delete.
4. In the window that appears, click OK.