Gu's teammate Son Hee Jong finished second while Anne Arnouts of Belgium took the bronze.
"The weather was hot," said 26-year-old Gu, "but that was fair with every athlete, so I was satisfied with the result."
Gu, who majored in sports in a local university, spent 3-5 hours per day on training. She missed the opening ceremony on Friday because of the early starting time of her event.
"I was a little bit disappointed about that," said Gu, "but I watched TV and that's also very good."
Aizhan Zhaparova of Russia was seen as a major favorite before the race. As a Russian national champion, she was ranked 93rd on the UCI (Union International de Cyclisme) world ranking list. Zhaparova led the team in most parts of the race, only to find the seventh berth due to the poor performance on the sprinting stage.
The weather was sunny on Saturday, which increased cyclists' energy expenses. Several riders didn't finish their race, including Chinese Taipei athletes Huang Tingying and Lee Yuhsuan.
Arnouts, a collage student majored in pharmacy, said she felt a little nervous before the race.
"A little stressed before the race," said Arnouts, "because I really want to perform well in the race."