Sun first represented China at a major international during the 2015 IPC Athletics World Championships in Doha, entering the shot put and javelin throw events. He finished fifth in the shot put, but finished on the podium in the javelin, throwing a new world record with a distance of 43.67 metes to take the gold medal. The following year he qualified for his first Paralympic Games, representing his country in the javelin at Rio de Janeiro. Sun was unable to replicate the form he had shown in Doha, but his best throw of 41.81 was enough to win him the bronze medal.