The defending champion charged down the course in one minute 13.14 seconds with Norwegian Aksel Lund Svindal taking second place 1.30 behind.
Ligety, who has already won the super combined and super-G events, would become the first man to win three golds at the world championships since Frenchman Jean-Claude Killy in 1968.
Overall world Cup leader Marcel Hirscher of Austria, who has been struggling in Schladming, managed third place, one hundredth of a second behind Svindal.
"I had a strong run, I didn't take all risks but I certainly going for it," Ligety told reporters.
"It was really challenging, the most important was to keep the ski under great control as it was easy to make a mistake on that icy snow."
The second leg is due to start at 1230 GMT.