A great first half saw them run in three tries through Julie Billes, Audrey Forlani and GaŽlle Mignot as they dominated up front.
In the second half, a penalty try, followed by a second try from Forlani and an acrobatic finish by Elodie Poublan late on.
France started strongly with Safi N'Diaye and Coumba Diallo combining well to get in behind the Italian defence. Les Bleues spread the ball quickly and Poublan found Montpellier teammate Billes for the first try of the game. Audrey Abadie was unsuccessful with the conversion attempt.
After 15 minutes played, some excellent reading of the Italian lineout saw French openside Pauline Rayssac steal the ball and launch a dangerous looking attack resulting in Forlani crashing over for the second try.
Abadie missed the conversion again but France had their third try of the match with just 23 minutes played, a successful catch and drive from a lineout seeing captain Mignot cross the whitewash.
Then with just over half an hour played, Abadie was on target again with a penalty to take the lead up to 20-0 at the break.
With the second half underway, France almost immediately scored with Billes making a break from inside her own 22, kicking ahead but just failing to keep her following kick in play with the try-line begging.
With just under 50 minutes played, The French pack's dominance paid off when referee Sara Cox awarded them a penalty try after a number of five-metre scrums. Abadie added the extra two points with the conversion making it 27-0.
And with an hour gone Forlani collected her second try, bursting through from a ruck to stride over, with Abadie again successful with the conversion.
With nine minutes remaining Poublan finished another great move, collecting the ball from Caroline Boujard, deflected off an Italian hand, before finishing in the corner.
France will now turn their attentions to a huge game against defending champions Ireland in Perpignan, while Italy will host England.
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England defeated New Zealand 49-46 to level up the three-match Series at 1-1 heading into the deciding match on Wednesday morning.
Sloane Stephens advanced to her first Grand Slam final at the US Open on Thursday night