Miller was well ahead of the field from the first split time before finishing the challenging Streif course in 2 minutes, 2.93 seconds.
Overall World Cup leader Aksel Lund Svindal came 0.96 back in second, while third-place Hannes Reichelt of Austria finished a massive 2.35 seconds behind the American.
"I've been focusing on this race all year," said Miller, who finished runner-up in 2008 and '11 but has yet to win the downhill in the Austrian resort. "I know it's hard to win here. I've put a lot of energy in being ready here ... And I think I had fast skis today, too. Obviously on this track you can't do much if your skis are not running."
Last year's winner Dominik Paris of Italy and Olympic downhill champion Didier Defago of Switzerland shared 10th, trailing Miller by 3.21 seconds.
It was the only training run before Saturday's race after mild temperatures softened the snow and made runs earlier this week impossible. Organizers had to change the bottom part of the course to avoid the Hausbergkante, one of the marquee sections, where snow conditions were still insufficient.
Miller mastered the steep upper section by choosing a different race line, allowing him to take more speed coming out of the Steilhang curve.
"I was higher through the Steilhang and exited it much better than where the tracks were," Miller said. "The tracks were done before me, no one was up high where I was. That makes a huge difference. You cut off the line but you also carry speed onto the road."
Miller drew praise from his competitors, who acknowledged they had been left with some homework before Saturday's race.
"Bode was fantastic," Reichelt said. "My run wasn't great and I am definitely going to watch a video of Bode's run."
His Austrian teammate Max Franz added "Bode had a very clean run. We have something to analyze."
Christof Innerhofer, who is chasing his first downhill podium of the season, said he was unable to ski like Miller did.
"He is crazy, he raced a killer line. I tried that line as well but I just didn't succeed," the Italian said. "I am not having a great season so far. But I felt well on the snow today and I want to attack here."
Even Svindal, winner of two downhills and two super-G races this season, said he was going to study footage of Miller's performance.
"You know Bode can pull off that kind of thing," the Norwegian said. "When I think about my run, I am not surprised that someone can be a lot faster from the top. I wasn't able to stick to my plan because I got bumped out of my line. I have the speed but I need to clean up the first part. I will definitely watch Bode's run on video."
The changed bottom section caused many racers troubles. Where they usually go right into the Hausbergkante coming off a fast straight part, they now faced a sharp left turn left.
To Miller, it didn't make much of a difference.
"It's a different set of skills that's tested," the American said. "The cool thing is no one skies that so it's pretty even for everybody. No one has had a change to ever have a run like that so I think it's OK."
Saturday's race is the penultimate downhill before the Olympic race on Feb. 9.
The Hahnenkamm event starts with a slalom Friday and concludes with a super-G and a super-combined race Sunday.