China has nine medals in six days of competition at the worlds, all in diving.
"After the semifinal I knew I could get much better in the final," said Guo who won the 3m springboard in Fukuoka in 2001 and also took the silver in the 2000 Sydney Olympics.
"I had great confidence and I gave every dive my best," she said.
China won eight golds in diving in Fukuoka, and the five golds in Sydney.
"We are the strongest divers in the world and we expect to get more medals in the coming events," said the 22-year-old gold medalist. Guo led throughout the final session of five dives. Wu got the highest score with 83.70 in her final attempt, a reverse 2 1/2 somersault pike.
China won its second gold medal in diving when Xu Xiang took the men's 1m springboard. Its first gold came on the opening day when women's platform star Lao Lishi and Li Ting won the 10m synchronized competition.
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