The coast guard said another commando was injured in the attack by Chinese sailors suspected of fishing illegally in the Yellow Sea off Incheon, west of Seoul, the Yonhap News Agency reported.
The dead guard member, a 41-year-old corporal, allegedly was stabbed with glass fragments wielded by a Chinese fisherman and died while being taken to a hospital in Incheon, the news agency said.
The injured commando suffered wounds to his stomach and was being treated at the Incheon hospital, Yonhap said.
The report said the coast guard commandos were trying to gain control of the vessel when the attacks occurred Monday morning about 52 miles off Socheong Island.
The vessel, with nine sailors, was later seized.
The South Korean coast guard has been patrolling the region to stop frequent incidents of illegal fishing by Chinese fishing vessels, Yonhap said.