She finished in 36th place with a time of 1.33:36, remarkably faster than the previous national record she set at 1.35:15.
Thanh Phuc, from the central city of Danang, competed in the race against 61 other athletes.
The gold medal went to Elena Lashmanova from Russia with a time of 1:25.02, Olga Kaniskina from Russia took silver after 1.25:09 and China’s Shenjie Qieyang earned the bronze with a time of 1.25:16.
Phuc was the last Vietnamese athlete competing in the world’s largest sporting event.
Vietnam has sent 18 athletes to London this time hoping to have its name listed in the medal tally. However, none of them won a medal.
The country's best results were fourth place in weight-lifting and shooting.