Hyun-Soo began skating in primary school. Watching the victories of Jee-Hoon Chae and Dong-Sung Kim at the Olympic Winter Games in Lillehammer in 1992 and Nagano in 1998 pushed him to improve further and become a great short-track speed skater.
In Salt Lake City in 2002 his best performance was fourth place in the 1,000 meters. He was caught up in a collective fall on the final bend, impeding him from reaching a better result. The young skater was disqualified fro the 1,500 and the 5,000 meter team events. Following the disappointment at the Olympic Games he went on to win four consecutive world championship titles.
The Korean skater was one of the favourites at the Olympic Games in Turin in 2006. He won the 1,500m and 1,000m races both times ahead of his compatriot Ho-Suk Lee. A few days later the South Korean team won the men’s 5,000 meter relay only forty-five minutes after Ahn had suffered his only defeat in Turin, finishing third in the 500m race.