The dual defending champion continued his recent owning of the world No.7 to win 6-3 6-4 6-4 in another one-sided quarter-final at Melbourne Park that lasted two hours and 23 minutes on Wednesday.
World No.2 Sinner will meet 10-time Open champion Novak Djokovic in a blockbuster semi-final, a rematch of their 2024 meeting, on Friday.
Djokovic, who has benefited from a walkover and a retirement to progress to the final-four, is the only man to win three-straight Australian Open titles in the professional era.
Sinner is on a 19-match winning streak at Melbourne Park, having lost at the first major of the year back in the fourth round of 2023.
After losing his first match against Shelton in Shanghai three years ago, Sinner has more than made up for that defeat by winning the next nine matches without dropping a set.
The big-hitting left-hander wasn't disgraced, but never looked like ending Sinner's 22-straight set stranglehold on him.
The Italian ace, who struggled with the heat in his third-round win over Eliot Spizzirri, appeared to be battling physically in between points during his demolition of Shelton.
But Sinner was still close to his best, setting him on a collision course for another final against arch-rival Carlos Alcaraz.
"I was struggling (in the third round)," said Sinner, who brushed off any lingering concerns about his health.
"But we go day-by-day.
"I had a great win a couple of days ago against a fellow Italian (Luciano Darderi), which gives you this good confidence boost.
"Today I felt like I was moving again a little bit better.
"I feel stronger physically again, so I'm very happy."
Sinner and Alcaraz faced off in three grand slam finals last year, with the Spaniard winning 2-1 with victories at Roland Garros and the US Open but losing at Wimbledon.
Only the top-four players at Melbourne Park remain, with world No.1 Alcaraz to come up against fourth seed Alexander Zverev in the other semi-final.
Sinner will play Djokovic for the fifth time in a grand slam semi-final, having won the past three, including last year at the French Open and Wimbledon.
Meanwhile, a disappointed Shelton was licking his wounds, but refusing to be broken by the experience of continually coming up short against Sinner.
"My level is better, and I'm getting better and better and becoming a lot less limited," Shelton said.
"This game takes time, and the results don't always come when you want them.
"I'm getting to the point now where I'm getting stopped up by the toughest challenge in the game for the most part, and I do think that I'm close to bringing it all together.
"I think it's just going to take that one time where I do do it to kind of get me over the hump.
"Certainly not discouraged from a performance like this."
