The result put the champions on 73 points from 30 games, 11 ahead of Monaco who host third-placed Lille on Sunday.
The only downside for coach Laurent Blanc's PSG came when captain Thiago Silva left the field midway through the first half after sustaining a facial injury in a mid-air clash with Lorient forward Vincent Aboubakar.
The Brazil centre back was replaced by compatriot Alex who sparkled alongside Marquinhos in defence.
PSG, who were drawn against Chelsea in the Champions League quarter-finals earlier in the day, went ahead four minutes before the break when Zlatan Ibrahimovic's shot was parried by Fabien Audard into the path of Motta and he poked the ball home.
Ibrahimovic went close seven minutes into the second half but Audard tipped away the Sweden striker's fierce effort from 20 metres.
Blanc brought on Yohan Cabaye on the hour after midfielder Marco Verratti picked up a yellow card and the substitute blended in well with the rest of the team.
Lorient's Bryan Pele beat keeper Salvatore Sirigu in added time but his goal was ruled out for offside.
- Sports & Recreation
- Laurent Blanc
- Thiago Silva
- Fabien Audard
- Zlatan Ibrahimovic