Upon graduation from Gwangju Jeil High School,[1] Sun joined the Korea University baseball team in 1981.

He led Team Korea to its first champion in the event, posting a 0.31 ERA in 29.0 innings pitched and racking up 3 complete game wins.

In August 1984, Sun competed for the South Korea national team in the 1984 Los Angeles Summer Olympics, where they finished 4th in the baseball tournament.

Signed by the Haitai Tigers, Sun made his debut in the KBO league against the Samsung Lions in Daegu on July 2, 1985.

In 1993, his first full season as a relief pitcher, Sun finished with a 10−3 record, a league-leading 31 saves, and 164 strikeouts in 126.1 innings pitched.

However, Sun came back strong in 1995, leading the KBO league with 33 saves and recording a 0.49 ERA in 109.1 innings pitched.

After the announcement, the Chunichi Dragons and Yomiuri Giants in NPB swiftly attempted to acquire him to fill bullpen void.

In December 1995, Sun managed to sign a contract with the Chunichi Dragons on a four-year loan deal from the Haitai Tigers.

During his inaugural NPB season, Sun struggled to adjust himself to Japanese style of play, and was sent down to the reserve team of the Dragons several times.

in 1999, Sun notched 28 saves (the league's runner-up) and a 2.61 ERA, and allowed only one home run, appearing in 39 games.

Amid controversy, Sun announced retirement on November 22, 1999 after he finally failed to sign with the Dragons.

Meanwhile, the Haitai Tigers in the KBO also planned to set his final game with a ceremony in Gwangju, South Korea.