Abstract: To understand the effects of petroleum hydrocarbon pollution on growth, reproduction and development of aquatic organisms, the acute and chronic toxicities of lubricating oil to water fleas Moina mongolica were studied under conditions of lubricating oil pollution.The results showed that the LC₅₀ was found to be 7.98 mg/L in 24 h, in 5.81 mg/L in 48 h, 4.99 mg/L in 72 h, and 3.04 mg/L in 96 h, with safe concentration of 0.92 mg/L.The chronic toxicity test revealed that the minimal survival time and survival rate were observed in the water fleas exposed to lubricating oil at a dose of 18 mg/L.However, there was no significant change in reproduction and population increase parameters of the water fleas in the test concentrations, indicating that the low concentration of lubricating oil has relatively weak toxicity to the water fleas.