He won the bronze medal in the 50 metre pistol competition at the 2004 Summer Olympics held in Athens.

Three days later, he then competed in the 50 metre pistol event, where he scored 563 and 660.2 points for qualification and final rounds respectively, thus earning a silver medal.

Kim was stripped of his two medals from the 2008 Summer Olympics, making Kim the second athlete, and first medal winning athlete, to test positive for a banned substance at the 2008 Olympic Games.

In the 10 metre air pistol, the bronze medal went to Jason Turner of the United States.

[5] On August 15, the day when Kim Jong-su officially had his medals revoked, the KCNA reported: Kim Jong Su placed second in the men's 50 metre free pistol and third in the men's 10 meter air pistol.