Abstract: Zebrafish was used as a model organism to study the effects of γ-ray irradiation on the developmental morphology of important organs in the aquatic organisms. Different doses of gamma rays (0.25, 0.5, 1 Gy) at the dose rate of 47.79 cGy/min were used to irradiate zebrafish embryos at early development stage (5 hours post-fertilization, 5 hpf). The changes of yolk sac area at 3 days post-fertilization (3 dpf) and the changes of the morphology of liver, spleen and pronephros at 3 dpf and 5 dpf after γ-ray irradiation were analyzed, respectively. It is found that the area of yolk sac in larval zebrafish at 3 dpf increases with γ-ray irradiation dose in a dose-dependent manner. The vacuoles increase and some cavities occur in liver of larval zebrafish at 3 dpf. The developmental morphology of liver in larval zebrafish at 5 dpf is abnormal, including the reduction in liver size, the increase of vacuoles in liver cells, the deformation of hepatocyte nucleus, the relatively small hepatic sinusoid and the deformation of nucleated erythrocyte and so on, but the developmental morphology of pronephros and spleen are normal. The ultrastructure of liver cells at 3 dpf shows that γ-ray irradiation can impair mitochondria of liver cells, broaden the intermembrane space of cell nuclei, spoil the arrangement of rough endoplasmic reticulum and so on. The results show that γ-ray irradiation can inhibit the absorption of the yolk in embryos in a dose-dependent manner and change the microscopic and submicroscopic structure of the livers in embryos.