Song moved up a weight class from half-middleweight to middleweight in 2012 after constant defeats to teammate Kim Jae-bum and inability to qualify for the Olympics in 2008.

Song served in the Republic of Korea Armed Forces as a sergeant, and represented them at the Military World Games in 2003, winning gold in the lightweight category.

Song's first high-level tournament was at the 2006 Jigoro Kano Cup in Tokyo, but lost to Japan's Hirotaka Kato in the final, settling for silver.

He competed at the Super World Cup Tournoi de Paris a month later, losing to Italy's Giuseppe Maddaloni for his third consecutive silver.

Song's second tournament would be a turning point in his career, as he lost to local half-lightweight number one and eventual 2008 Olympic silver medalist Kim Jae-bum at the Korea National Qualifiers in the finals by shido in golden score.

In 2010, Song competed in his first Masters at home ground in Suwon, but failed to medal, losing his second fight to Russia's Sirazhudin Magomedov by ippon.

His losses continued to mount in the high level competitions, as he finished seventh at the Grand Slam in Paris, failing to defend his title.

At the Grand Prix in Düsseldorf, Song again failed to medal, losing to prime rival Kim by waza-ari in golden score, after nearly eight minutes, in the semi-final.

[14][15] Song won another silver medal at the Grand Slam in Moscow, losing to Russia's Ivan Nifontov with harai goshi by ippon in the final.

In his second World Championships, he again crashed out early, losing to Brazil's Tiago Camilo narrowly by yuko in golden score.

He then lost in the semi-final at the Grand Prix in Abu Dhabi to rising Georgian star Varlam Liparteliani by ippon in just 47 seconds.

His medal-less streak continued at the Grand Prix in Qingdao, narrowly losing to Mongolia's Enkhbat Erdenebileg by two yukos in the round of sixteen.

[27] Under Song, Korea has produced two world champions with An Baul and Gwak Dong-han, and bronze medalists Kim Won-jin and An Chang-rim.