The Italian powered to a 6-3, 6-3 win over his fifth-seeded opponent and will next face either Alexander Zverev or Daniil Medvedev in Saturday's semi-finals.
Sinner, looking to take advantage of rival Carlos Alcaraz's shock second-round loss to Cameron Norrie, extended his winning streak to 24 successive matches on indoor hard courts.
Sinner will usurp Alcaraz at the top of the rankings by winning the title at the La Defense Arena.
"At the moment I'm not thinking about the ranking," he said.
"It all depends on how I'm playing. We go day by day, every day you have very difficult challenges coming up."
He has now won seven successive matches against the powerful Shelton since losing their first meeting in Shanghai in 2023.
The 24-year-old is targeting his fifth title of the season after last weekend adding the Vienna Open trophy to his Australian Open, Wimbledon and China Open triumphs from earlier in the year.
Sinner has won his last three meetings with both Zverev and Medvedev.
"I'm happy to be in the situation where I am, tomorrow it's again a very important day but I'm looking forward to it," Sinner added.
The four-time Grand Slam champion wrapped up the first set in just 34 minutes, sealing it with a thumping baseline winner to break Shelton's serve for the second time.
A 22nd consecutive win against American opponents appeared nothing more than a formality for Sinner when he moved 3-1 up in the second set.
But Shelton immediately hit back with a break to love before levelling the set to gain a foothold in the match, much to the delight of a packed crowd.
The left-hander's revival did not last long, however, as Sinner broke again in the eighth game.
A deft winner at the net secured a place in his 13th Masters semi-final on his first match point.