In four 30-minute bouts against the league team, the hosts found the net with doubles from Danny Ings and James Ward-Prowse, who celebrated their two calls in England last week.
Che Adams, Nathan Redmond and Ryan Bertrand also hit the target in the first hour.
With both sides reshuffling the rosters, Swansea responded with Jay Fulton with 10 minutes left, but Ralph Hasenhuttl’s side won convincingly.
It only took the Saints six minutes to take the lead as Bertrand leaped forward to catch Alex McCarthy’s ball at the top.
The left-back had the easier task of making ends meet with Adams, who did not fail to end his preseason.
It took only seven more minutes for Hasenhuttl’s side to double their lead.
Oriel Romeu won the ball in a danger zone before Redmond shot home.
Forward Ings then continued his hot 2019-20 form when he shot at home after Stuart Armstrong suffered a foul in the area.
Unchanged in the second quarter – it was then the turn of skipper Ward Prowse to insert a penalty for the 4-0. He sent the keeper in the wrong direction after Redmond was shot.
Bertrand then entered the scene when he landed a powerful shot that flew over the crossbar.
In the 42nd minute, former Chelsea player Bertrand turned supplier to help Ings win his second.
Controlling the defender’s pass, the frontman moved onto his right foot before healing in the far corner of the net.
Ings was then selfless after coming out clean and making ends meet for Ward Prowse to add his second and seventh Saints.
The two teams then changed their rosters for the third and fourth quarters.
Swansea struck out a goal when Fulton rushed in to make it 7-1 after the ball hit the post.
First and second 30 minutes: McCarthy.
Walker-Peters, Stephens, Bednarek, Bertrand; Romeu, Ward-Prowse, Armstrong, Redmond; Adams, Ings.
Third 30 minutes: Forster; Valery, Vestergaard, Klarer, Vokins; Slattery, Smallbone, Djenepo, Boufal; Long, Obafemi.
Fourth 30 minutes: Forster; Valery, Vestergaard, Klarer, Vokins; Jankewitz, Smallbone, Djenepo, Boufal; Long, Obafemi.