Trentin was one of four Quick-Step riders in a 15-rider move that emerged towards the end of the Belgian one-day race, and he made the most of his team's superiority.
The Italian star accelerated inside the final 6.5 kilometres, with BMC’s Jempy Drucker was the only one to go with him.
Trentin, not happy to simply wait for a two-up sprint, then attacked again with a couple of kilometres remaining, comfortably riding away from Drucker through the technical finish to the race, giving himself enough time sit up and celebrate the win as he crossed the line.
Drucker took second place, while Andre Greipel (Lotto Soudal) lead the bunch sprint for third. the German having been part of the peloton that caught the remnants of the front group soon after Trentin and Drucker had attacked.
"It was a really nice race today," said Trentin. "Together with Fernando (Gaviria), we asked the guys to make the race hard and they split the field in the final hour of racing. Once the selection was made, we had four riders in the group and that was the perfect situation for us.
"With five kilometres remaining, I wasn't going for an attack, my only intention was to pull hard knowing the chasers were coming back, but after getting a gap together with Drucker, I decided to continue.
"I was aware he too was fast and after a long race you can never know what will happen, so on that bridge I gave it a try and fortunately I dropped him, soloing to this nice win, which bodes really well for the World Championships."
Trentin is a key part of the Italian squad for the Road Race, who will go into the Bergen course with a number of strong options, but it looks inceasingly like Trentin will be their leader for the event.
SBS's coverage of the UCI Road World Championships begins Sunday September 17 with the Men's and Women's Team Time Trial starting from 8pm AEST.