Victory was achieved with a goal in the 68th minute by the 23-year-old forward Tiffeny Mibrett, whose first international cap was against China five years ago.
Midfielder Shannon MacMillan had put the Americans ahead in the 18th minute when she scored from close range following a deflection.
China's Wen Sun equalised in the 32nd minute with a chip over advancing keeper, Briana Scurry, the defender Brandi Chastain just failing to clear the ball off the line.
"I do feel some relief," said the American coach, Anthony Dicicco. "I certainly didn't want to let our fans down. Every game was difficult." The official attendance was 76,481 people - the biggest ever recorded to watch a women's match in the States.
Earlier, barely 24 hours after Brazil saw its men's team fail to reach the Olympic final after losing 4-3 to Nigeria in extra time, the Brazilian women's side went down 2- 0 to Norway in the bronze medal match after having a goal disallowed.
Midfielder Ann Aarones scored the first goal in the 21st minute, slotting the ball calmly past Brazilian keeper Meg, and then blasted home a second just three minutes later.
Brazil came out with renewed deterination in the second half but had their hopes dashed in the 51st minute when a goal by Roseli was disallowed for handball.Reuse content