France's Matuidi headed home a Zlatan Ibrahimovic cross following a quick counter-attack on the stroke of half-time to send PSG level with Lyon on 35 points but top on goal difference.
Lyon only threatened PSG when a Lisandro Lopez volley hit the post in the 27th minute and the big-spenders deserved their victory, proving much stronger than the visitors.
"Lisandro's chance could have changed the match but then we played at a very, very high level in the second half," PSG right back Christophe said.
"You don't have to get overexcited when everything is fine nor be depressed when you have bad times. All the squad just enjoy being first."
Lyon's Michel Bastos confirmed PSG's superiority but said his side would not surrender in the title race.
"It's a long way to go in the league. We know who are the favourites are but we will try to fight until the end," the Brazilian winger said.
Both sides are level on points with third-placed Olympique Marseille, who won 1-0 at Toulouse on Saturday.
The trio have a five-point lead over Lorient, who outclassed hosts St Etienne to clinch a 2-0 victory to climb up to fourth.
At Parc des Princes, Lyon had the early possession but the first attempt on target was for PSG's Javier Pastore, whose shoot from close range in the 12th minute was parried away by Remy Vercoutre.
Lisandro Lopez went closer to scoring when he struck the post, without knowing at the time it was to be his side's only clear-cut chance throughout.
Thiago Silva was perfectly marshalling the home defence and Matuidi kept harassing the midfielders.
PSG eventually broke the deadlock when Ibrahimovic, who had been quiet, set up Matuidi for the opener just before the break.
The Swede, who has scored 17 and set up four of PSG's 33 league goals so far, could have doubled the lead a minute later but Vercoutre denied him.
The visiting goalkeeper then had to produce a solid performance in a one-sided second half.
The 32-year-old, who has been the first choice at Lyon this term for the first time since he joined them in 2002, saved Pastore's superb strike in the 65th minute.
He then won a one-to-one against Ezequiel Lavezzi nine minutes from time but his team-mates never managed to really push for an equaliser.
At St Etienne, Lorient extended their winning run to a fourth game thanks to Jeremie Aliadiere's seventh goal of the season in the 20th minute and a Alain Traore header 18 minutes later.
Les Verts, whose goal drought has now lasted for more than 500 minutes, are eighth with 27 points.
Earlier, Henri Saivet rescued a point for 10-man Bordeaux as he struck home in the 76th minute to earn his side a 1-1 draw at basement side Nancy.
It was the fourth consecutive league draw for Bordeaux, who are seventh on 28 points, and the sixth in a row for Nancy, who wasted a lead in five of those games. Nancy have 11 points.