Abstract: All areas were investigated in Tianquan conunty to find out where Cystoathyrium chinensis was scattered. By focusing on three methods of survey:line-intercept,quadrat sampling and habitat investigating,it was known that Cystoathyrium chinensis was distributed in the Tuanniuping,Erlang Mount,Tianquan County,growing at both sides of the gulch. Its main features were as follows:very narrow distribution range and extremely sparse guantity. Besides,its habitat conditions were special and biotic potential was low. The major reasons causing the endangerment of Cystoathyrium chinensis displayed the following sides:the plant itself had many biological disadvantages,the growing environmental conditions were very rigorous and its competitive ability with other species was weak,etc. Based on its resource status and endangered mechanism,some appropriate suggestions were proposed like initiating widely propaganda and educational work,strengthening the protection of existing resource,off-site preservation,and building extremely small population of Cystoathyrium chinensis,etc,to protect it.