In May 2007, Son first competed in the World Taekwondo Championships in Beijing, China at the age of 19, but lost to Algimiro Mejias of Venezuela in the bantamweight (-62 kg) first round.

On August 21, 2008, Son won the gold medal in the -68 kg category at the 2008 Olympic Games in Beijing, defeating Mark López of the United States in the final.

[1][2] On July 22, 2009, Son was knocked out by Park Hyung-Jin in Round 2 of the featherweight (-68 kg) final match at the 2009 President's Cup in Ulsan, South Korea via a back spinning hook kick.

Due to the defeat, Son didn't qualify as a member of the 2010 South Korean national taekwondo team.

In 2010, Son won the gold medal in the World Combat Games by defeating Reza Naderian in the final.