The peak of Sun's career was the 1994 track and field season. He began with a national title win in the 5000 m at the Chinese Athletics Championships. He was entered for both this event and his steeplechase speciality at the 1994 Asian Games. He won the bronze medal in the 5000 m, beaten by Japan's Toshinari Takaoka and Ahmed Ibrahim Warsama of Qatar by a margin of less than one second. He was the clear gold medallist in the steeplechase, setting an Asian Games record of 8:31.73 minutes – a full two seconds clear of Saudi athlete Saad Shadad Al-Asmari. This record stood until the 2002, when it was bettered by Qatar's Kenyan-born runner Khamis Seif Abdullah. It was the last major medal of Sun's international career.