The horseshoe crab, Tachypleus tridentatus, is known as a living fossil. It plays a very important role in evolution and medical resarch. Horseshoe crab once is attributed 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. Horseshoe crab 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 April 6 to August 11, and spawning peak period was August ( 54%). Spawning period water temperature range was 20.2℃ to 30.2℃. We finally collected 90,364 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 2,408 1st instar larvae 、388 larvae molted to 2nd instar stage、112 larva molted to 3rd instar stage. In October 11 2008, among of them 10 individuals were successfully molted to 4th- instar larvae (after hatching 138 days) and still alive.