She was active as a speed skater between 2007 and 2017. Su-Ji represented her nation at international competitions. She participated at the 2012 Winter Youth Olympics and ISU Junior World Cup Speed Skating events, where she won a team pursuit event in January 2016 in Baselga di Piné. At elite level she competed at the 2017 Asian Winter Games in the 1500 metres event, finishing 11th. Between 2012 and 2017 she had a total of 14 starts at national championships and won the bronze medal at the 2016 South Korean Allround Championships.