It was the second goal medal of these Games and the sixth of her career. She had been tied with China's Fu Minxia and American Greg Louganis for the most diving medals all time.
Guo won the event with 415.35 points. She had teamed with Wu Minxia to win the springboard synchronized gold medal earlier in the Olympics.
"Today must be the most memorable moment in my life," she said. "I love this sport and I'd like to go on diving if I can."
Julia Pakhalina of Russia won the silver with 398.60 points. Wu took bronze with 389.85
Americans Nancilea Foster and Christina Loukas finished eighth and ninth out of the 12 divers who qualified for the final.
China has won all five of the diving gold medals awarded thus far at the Olympics and is heavily favored to win the three remaining.