[Aim] Mineral oil emulsion is widely applied for pest control on fruits, vegetables, crops and gardens because of low human toxicity, broad insecticidal spectrum and lack of resistance. However, there are few reports about the effect of mineral oil emulsion on natural enemies. Information on the safety of mineral oil emulsion on natural enemies in different development stages can provide abasis for better coordination of chemical and biological control methods.[Method] Residual film method and dipping method were adopted under laboratory condition to determine the impacts of mineral oil emulsion on the hymenopteran natural enemy, Aphidius gifuensis in different development stages.[Result] Mineral oil emulsion had little influence on adult A. gifuensis, without obvious toxicity when consumed, but with a certain contact toxicity. Under the highest treatment concentration of 150 dilution multiple liquid (4986.960 mg·L^-1), modify the survival rate was 92% after 24 h. The oil emulsion can cause higher mortality to eggs and larvae of A. gifuensis with the LC₅₀ being 859.541 mg·L^-1, which is much lower than the lowest tested concentration of 450 dilution multiple liquid (1662.320 mg·L^-1). Compared to the control group, the parasitoid emerged from emulsion-treated mummified aphids 1 day later, and the emergence rate decreased with the increasing treatment concentration, from 81.25% at the 450 dilution multiple liquid to 47.75% at 150 dilution multiple liquid.[Conclusion] Mineral oil emulsion can be used when adult A. gifuensisare present, but its specific concentration and application time remain to be determined further to minimise damage to immature stages of this natural enemy.