This paper studied the effect of ammonia nitrogen and sulfurated hydrogen on the larvae of penaeus japonicus. The grades were designed by equal space between logarithm, and the median lethal concentration was computed by Linear Regression. The results showed that ammonia nitrogen and sulfurated hydrogen had a notable toxic effect on the larvae of penaeus japonicus(F>F_ 0.05), and the mortality rate of larvae increased significantly with the concentration. The endurance to two toxicants in all larvae stages was different, and the endurance of the nauplius was better than that of the zoea larvae and less than that of the mysis larvae and postlarvae. The safety concentration of ammonia nitrogen on the zoea larvae, mysis larvae and postlarvae was 0.295 mg/L, 0.724 mg/L, 1.072 mg /L respectively, and that of sulfurated hydrogen was 0.043 0 mg/L, 0.055 3 mg/L,0.070 5 mg/L.