The 24-year-old pounced with two first-half goals to ease the Welsh side into fifth place in the table as managerless Wednesday floundered.
It saw Wednesday - with Academy boss Sean McAuley in temporary charge - booed off at the break and already looking like a beaten side - followed by an encore at the end of the game.
It was Pratley who grabbed the glory, doubling his tally for the season and producing a five-star performance.
It was a dream start for Swansea but a nightmare for Wednesday, now without a win in ten, as they were over-run by a five-man midfield.
With only five minutes gone Wednesday were caught out when Gorka Pintado chipped in a clever ball leaving Darren Purse and Mark Beevers flat-footed.
As the home side were exposed Pratley ran through unchallenged to meet the pass and slotted an accurate ball wide of Lee Grant's despairing dive to his left.
The setback sparked Wednesday into life and, as they looked for a reply, Jermaine Johnson cut in from the left and unleashed a fierce 25-yard shot that brought a fine save from Dorius de Vries.
From Darren Potter's corner captain Purse outjumped the defence but his towering header was well saved. As Wednesday produced a spell of promising pressure Swansea broke smartly and the home side were caught on the hop again.
Andrea Orlandi's accurate pass sent Nathan Dyer scampering past the hapless Lewis Buxton to fire a low pinpoint cross and Pratley, unchallenged, accepted the invitation and slotted a crisp side-foot shot past Grant from 15 yards for his second.
Wednesday should have pulled one back after 65 minutes when Swansea conceded a free-kick just outside the area. Potter swung in a dangerous cross but Purse failed to connect when he looked to have a clear heading opportunity.