In April and May 2010, two survey cruises were carried out in Nansha islands by lightpurse seiner. The result shows that: a total of 18 species were caught, major species include Decapterus maruadsi, Symplectoteuthis oualaniensis, Gymnosarda unicolor , Euthynnus pelamis and Caranx ignobilis etc. The maximum catch reaches 5.05 t, catch per net(CPUE) was 1.256 t/net , mean catch rate was 154.95 kg/h. Yongshu and Chigua reefs have higher catch and catch rate than other areas. Different species and catch happened in different reefs and months. Tuna was caught only at Yongshu and Chigua reefs. We need more research in other places and seasons.