Jiao, a silver medalist in the event at the Beijing Games, swam a time of 2:04.06, while Mirieia Belmonte Garcia of Spain took silver, with 2:05.25. Japan's Natsumi Hoshi finished in 2:05.48 to clinch the bronze medal.
Kathleen Hersey of the United States narrowly missed the podium with a time of 2:05.78. Compatriot Cammile Adams finished fifth, while British hopeful Jemma Lowe took sixth.
Surprisingly, defending Olympic champion Zige Liu of China finished eighth with a time of 2:07.77, nearly four second slower than Jiao.
Jiao's victory gave China its fourth swimming gold medal of the Games thus far.