Wang, seeded 18th, did not manage to hit a single winner as she was taken apart in her first grand slam quarter-final.
It was the American's 100th career victory at the US Open and at 44 minutes was the match quickest at this year's tournament.
"It's really unbelievable," said Williams, 38. "When I first started here I was like, 16. I never thought I would get to 100 wins and still be here but I love what I do.
"When I'm playing someone I know is playing well I know I have to step up or go home, and I want to stay here."
Williams showed no ill-effects from rolling her ankle during her fourth-round win over Petra Martic.
"I'm feeling good," she added. "It's been a tough year but physically I'm feeling great and more than anything I'm just having fun when I come out here."
Williams, the eighth seed, will play in the semi-finals.
"She's had a great year," said Williams. "She made the semis at Wimbledon and I feel she wants to go one step further, so I feel I'll have to come out and play really well."
Svitolina, the fifth seed from Ukraine, beat Britain's Johanna Konta 6-4 6-4 over 100 attritional minutes.
She said: "I don't think that I was expecting going into this tournament that I'm going to make semis.
"I'm just taking one match at a time. It's a grand slam. There is lots of pressure, lots of expectations from people. But you also put lots of pressure on yourself.
"You have to just go out there, do your job and don't think too much what's going on around you, and who handle it the best wins.
"Definitely it's a big challenge to play against her. Obviously Serena is amazing champion. It's probably it's going to be really tough against her."