Williams, 37, overpowered the Ukrainian fifth seed to win 6-3 6-1, and is now aiming for her first Grand Slam win since giving birth in September 2017.
The six-time champion will face Swiss Belinda Bencic or Canadian teenager Bianca Andreescu in Saturday's final, both competing in their first major semi-final in Thursday's night session in New York.
Williams seemed to be free of her knee problem and back injury which had her left in tears in the final of the Rogers Cup in Toronto, handing the title to Andreescu earlier this August.
The American tennis star, known for her powerful physique, also came under heavy criticism for her outfit choices on the court at the beginning of the tournament, wearing a black body-tight and extra-short jumpsuit, prompting debates online. The outfit was dubbed “embarrassing” and prompted users to call for a dress code at the US Open like at some other Grand Slam tennis tournaments.