The horseshoe crab, Tachypleus tridentatus, is known as a living fossil. It plays a very important role in evolution and medical resarch. Tachypleus tridentatus once istributed widely along the west coast of Taiwan island decades ago. It is almost eliminated from the coast as a result of pollution and degradation. In Taiwan, Tachypleus tridentatus,can only be found in Kimmen and Penghu island. Tachypleus tridentatus in Penghu is facing survival crisis. Thus, conservation need to be done in no time. The objectives of this study are establishment of inducing wild horseshoe crabs natural spawning under the artificial environment. Spawning season began from June 6 to September 10, and spawning peak period was July( 53%). Spawning period water temperature range was 26.2℃ to 31.2℃. We finally collected 74,504 horseshoe crab’s eggs altogether in this spawning system to save labor. It’s further to research and develop the circulating water system of fertilized egg hatching- out system. It hatched out 18,460 1st instar larva and 471 larva molted to 2nd instar stage. Among of them 17 individuals were successfully molted to 3rd instar larva and still alive.