Alexei Grichin of Belarus topped the men's qualifying competition.
Leu is one of only two women who attempt a triple flip with three full twists.
She nailed it on her second run, earned a score of 99.42, and combined with her first-jump score of 103.74, she had the new record.
The old record of 200.21 was set by Xiaoou Ji of China in 1998.
"I didn't think gold medal, or world record or anything," Leu said. "I just wanted to do my jump."
"I really like this hillside," she added.
"I was looking forward to it, but it's always a new day. You have to go out and do it."
In a competition missing Jacqui Cooper and Emily Cook, Leu has set out her stall ahead of Monday's final.
Copper, of Australia, and Cook, America's top jumpers, are the only other skiers who include the triple-twisting triple in the repertoire.
The second-place qualifier, Alisa Camplin of Australia, finished with a score of 183.66, a full 19.5 points behind Leu.
In Cook's absence American hopes rested with Tracy Evans, but the three-time Olympian crashed out attempting a triple somersault.
Grichin, the reigning world champion, finished first of the 12 qualifiers in the men's competition, a dozen athletes that included four Americans.
Thay band of four was led by defending gold medalist Eric Bergoust finished second and hometown favourite Joe Pack was third.
The Czech Republic's Ales Valenta finished in eighth but will still be considered a real threat as he qualified without attempting his quintuple-twisting triple flip.
Nobody else attempts the jump and Valenta revealed that he may bring it out for the final on Tuesday.