Abstract: Based on otter trawl catch rates of five surveys conducted by South China Sea Fisheries Research Institute from 1961 to 1999, changes in demersal trawling fishery resources in the northern South China Sea were analyzed. The results indicated that, in over 30 years from early 1960s to late 1990s, the trawl catch rates have declined noticeably by 72% and 81% separately in the northern shelf and Beibu Gulf of the South China Sea. The catch rates have dropped by 71%, 74% and 70% respectively in the inshore, offshore, and outer shelf of the northern shelf. The demersal fishery resources in all areas of the northern South China Sea have been over-exploited, and more severe overfishing occurred in the inshore and offshore waters than in the outer shelf.