[3][4] He was granted exemption from South Korea's mandatory military service in 2010, following his gold medal victory at the Guangzhou Asian Games.

Kim was considered one of the Big Three Judokas of the -73 kg class in South Korea, along with Lee Won-hee and Wang Ki-chun.

But in 2007, he moved up in weight to avoid the fierce competition,[7] and won a gold medal in the -81 kg category at the 2008 Asian Judo Championships in Jeju.

In the gold medal match, he defeated two-time Olympic medalist Leandro Guilheiro of Brazil[9] by scoring a waza-ari with ouchi-gari in extra time.

[11] In the 2012 London Summer Olympics, Kim won the gold medal in men's -81 kg division, defeating German rival, Ole Bischof.