Lucas opened the scoring with a stunning effort before Jeremy Menez and Zlatan Ibrahimovic sealed the three points in the second half
Laurent Blanc's men headed into the game four points clear at the top of the table but will have been wary of a Reims team that was the last to beat them in the French top flight.
The defending champions have been in sparkling form since that 1-0 defeat back in March, and the capital club made no mistake on this occasion as they made it 25 league games without losing.
Lucas Moura opened the scoring midway through the first half with only his second goal in a PSG shirt, before Jeremy Menez's emphatic close-range finish doubled the advantage just before the hour mark.
Hubert Fournier's side wasted a host of chances, including a missed penalty from Grzegorz Krychowiak - scorer of the winning goal in last season's fixture - and it was punished by Ibrahimovic's late effort.
Edinson Cavani was left out of the PSG starting XI as Blanc made five changes to the side that beat Nice 3-1 prior to the international break, while Reims made four alterations from its 0-0 draw with Lorient, Gaetan Courtet named as the lone striker in attack.
After a quiet opening for PSG, Brazil international Lucas broke the deadlock as he powered a shot past Agassa after Ibrahimovic played him through on goal with a wonderfully deft pass that split the Reims defense.
The hosts offered little as an attacking threat for most of the half, but Sirigu had to produce another fine stop to keep out Mickael Tacalfred's deflected effort, before Marco Verratti cleared off the line after the Italian goalkeeper had fumbled a corner.
Still, it was PSG that continued to create the better opportunities, and it was denied once more by Agassa, who smartly stopped Menez's effort.
But, PSG did increase its advantage three minutes before the hour mark, Menez latching on to a clever pass from Verratti to fire home at the near post after Christophe Jallet had cut through the Reims midfield with a surging run.
Fournier's men pushed on and Mads Albaek was denied by the impressive Sirigu, who was not required to keep Krychowiak's penalty out as the Pole blazed over from 12 yards.
That proved to be to Reims' last real opening as PSG eased to a comfortable victory, which was sealed in bizarre fashion as Ibrahimovic shot into an empty net after Agassa's throw had bounced off Tacalfred.