Similar to deleting a vSwitch, when you choose to delete a port group make sure that the virtual machines have been reconfigured to use another port group which will provide them with network access.
A port group can be deleted by using either the vSphere Web Client GUI or the esxcfg-vswitch
command.
The following procedure explains how to delete a port group by using vSphere Web Client.
Select the ESXi host from the inventory, navigate to Manage | Networking | Virtual switches, and select the vSwitch from which would like to delete the port group.
Identify the port group from the switch diagram, click on the name of the port group, and click on the delete (X) icon to remove the port group:
Click on Yes to confirm the removal of the device:
The Recent Tasks pane should show the Remove Port Group task completed successfully.