The 23-year-old world number one and gold medal favourite lived up to her billing by beating Poland’s Sylwia Bogacka into second place.
Bogacka, 30, qualified in first place and was leading until the eighth shot, when a wayward effort condemned her to silver.
China’s Yu Dan collected the bronze medal with Beijing 2008 gold medallist Katrina Emmons fourth.
Yi, speaking after receiving her medal from International Olympic Committee (IOC) Chairman Jacques Rogge, said: ‘I’m very happy. I want to say thanks to China, to my mother and father.
‘I’m very excited and happy. I have been shooting since I was 13-years-old.
‘I’ve been up since 5am this morning. There was a lot of pressure on me.’