Gift Motupa grabbed an early lead for the Clever Boys in the third minute with a glancing header inside the box following a corner, 1-0.
Gavin Hunt’s charges were dominating the exchanges in the first quarter of an hour, while Usuthu were yet to settle in the match.
Mxolisi Macuphu had an opportunity to double the lead for the hosts in the 19th minute after going through on goal, but he fired his shot wide.
Macuphu eventually made it 2-0 for Wits with a close range finish in the 28th minute following a great run by Deon Hotto in the build-up.
The visitors were under siege even towards the end of the half and were lucky to head into the break trailing by two goals - it could have been more.
Thembela Sikhakhane almost pulled one goal back for Johnson’s men six minutes into the second stanza with a cracking strike that rattled the crossbar.
Usuthu were pressurising the home side getting chance after chance but were unlucky in front of goals.
However, Wits made it 3-0 with 20 minutes remaining in the half, with Scottish striker Simon Murray netting his first goal for the club.
In the end, there was no coming back of any sort from Usuthu who were simply outplayed and out-muscled by a classy Wits side.