Ctenogobius giurinus is a kind of small freshwater fish which propagates during April-June in the middle reaches of Jialingjiang in Nanchong.It has a egg-laying period of 2-3 hours,one copulation per interval of 1-2 minutes,egg-laying number of 30-50 per copulation,and total egg number of 1 000-1 600.The male C.giurinus is responsible for hatching eggs in most of the time,and the female hatches the eggs temporarily only when the male goes out to hunting for foods.The fertilized eggs were kept in a glass culture utensil during the observation.The results indicate that the fertilized and unfertilized eggs of C.giurinus have a group of sticky fiber on the one end which adheres to the gravel as well as other hard material.Their fertilized eggs are nearly spherical in shape and have a diameter of 0.453-0.644 mm,which are light yellow,translucent and very extensible.There are 1-30 oil globules in each egg,of which 1-4 are obviously bigger in volume.The eggs begin to inflate and become ellipse by absorbing water after 4 min of fertilization.According to the morphological characteristics,the embryonic development of C.giurinus may be divided into seven stages:the fertilized egg and the blastoderm formation stage,the cleavage stage,the blastula stage,the gastrula stage,the neural stage,the organogenesis stage,and hatching stage.Under the water temperature of 22.3-25.7℃,it requires 109 h 52 min for the embryonic development.The organs differentiation are highly degree before hatching,such as pectoral fin bud,gill plate,gas bladder,semicircular canal,evident mandible and geny-teeth.Newly hatched larvae have a total length of 2.485-2.640 mm and body height of 0.350-0.460 mm,which takes 4 days for the disappearance of the yolk sacs and 6 days for the disappearance of the oil globules after hatching.