Abstract: The fertilized eggs development of southern flounder Paralichthys lethostigma were observed and described. The incubation conditions were water temperature 18.50.5℃，salinity 32~33, pH 8.0~8.2, and flowing water with continuously aerating. The larvae hatched out at about 49h after fertilization and the larval mouths opened at 4th day and metamorphosis began at 26th day , completed at about 45th day after hatching. The laid eggs were floated with one oil globule. The gutswere thin, short and straight in the newly hatched larvae, then became longer and flexible during the larval development. At 3rd day the anus got through and 4th day yolk sac were completely absorbed. Melanophores occurred in the embryo 36h after fertilization in dispersal. Chrysanthemum-like melanophores were uniformly symmetrically distributed. During metamorphosis, the larval menanophores were replaced by adult menanophores on ocular side. There is no pigment exist on blind side. During the development before metamorphosis, crown-like larvae fin arose and was absorbed later. No swim bladder happened.