By interviewing local fishermen, we collected population status information of Horseshoe Crab (Tachypleus tridentatus)in the coasts of Zhejiang, Fujian, Guangxi, Guangdong and Hainan in the summer from 2006 to 2010 and we also visited 27 hatching sites in those coasts to survey the number of spawning adults and baby Horseshoe Crab hatched. We estimated the current resource of this species in Fujian by sampling them at 24 locations twice using shallow bottom trawling in summer 2006 and winter 2007, the results showed that local fishermen found out the population size of this species decrease greatly in most coasts of Zhejiang, Fujian, Guangxi, Guangdong and Hainan. No any spawning adults have been observed in the 27 hatching sites and few juveniles were found in 6 of the 27 sites. Fortunately at one more site (Zhangpugulei Fujian Province) we counted over 1 000 juveniles. The horseshoe crab almost disappears and is at the edge of extinction in most coast of China except for Dongshan Bay and Beibu Bay where a few Horseshoe Crabs have survived. However, the resource of Horseshoe Crab in the Coast of Kinmen Island of Taiwan has been recovered well due to artificial breeding and releasing, as well as the establishment of protected areas. The decline of Horseshoe Crab resource in China is mainly due to over-harvest, habitat destruction and marine environment pollution. This species is urgent to be protected. We suggest to include it in national key protection animals list, establish nature reserves at their hatching habitat, strengthen harvest regulation and conduct artificial propagation to protect this species.