Gut, 22, crossed the finish line in one minute 32.32 seconds, ahead of Austria’s Elisabeth Görgle and compatriot Fränzi Aufdenblatten.
Switzerland’s Fabienne Suter came fourth, 0.84 seconds behind the leader.
Gut's victory, her sixth this season, augurs well for the super-G race set for Thursday in Lenzerheide.
The Ticino native heads the World Cup standings for super-G this season with 348 points, ahead of her nearest rival Tina Weirather from Liechtenstein.
The downhill result means Germany's Maria Hofl-Riesch clinched the World Cup for the discipline this season, but her hopes of taking the overall crown were all but shattered by a bad fall.
Hofl-Riesch came to grief halfway down the course and was taken to hospital for a checkup on injuries to her back and shoulder.
The only rival who could pip her to the downhill World Cup, Austria's Anna Fenninger, could only place sixth when she needed to win the race to take the title.