Abstract: Embryonic development of Gobiocypris rarus was studied in 1990-1994, and 22 developmental stages were described and illustrated in this paper.1.The eggs are adhesive, nearly spherical,with a diameter 1.25-1.70mm,andthe diameter of the yolk is around 0.81-0.86mm.2.Newly hatched larvae have a total length of 3.90-4.50mm, with about 19+13 myomeres, well developed pectoral and gill arch, formed mouth and vent,emergence of air bladder and melanophores appearing almost all over the entirebody except on the marginal fin fold.3.The duration of elnbryonic development is prolonged largely by low temperature and accelerated by high temperature. The duration lasts about 204,106,88,75and 69hrs at the water temperature of 15.0, 20.0, 22.5, 25.0 and 30.0℃ respectively.4.A phenonmenon named “embryonic decidua” was observed from optic rudimentto tail vesicle stage of some embryos, in which a menbrance-like-structure surroun-ded a developing embryo and was finally burst by it. Since the phenonmenon hasso far not been recorded in any other species of fish and did not occur in all theembryonic development of G. rarus,questions about its origination and constructurewere discussed.