The optimum conditions of the supercritical CO₂ extraction of crude oil from schizochytrium were studied.Single factor experiments were conducted to investigate the effects of the ultrasonic pretreatment,humidity of raw materials and different carrying agents on the extraction rate of crude oil from schizochytrium.The results show,although the ultrasonic enhancement has little effect on oil yield,the reaction time is shortened by pretreatment.It is best to dry the microalgae powder before the experiment.Compared with methanol,ethanol and ethyl acetate,the methanol extraction rate was found to be higher than that of ethanol and ethyl acetate.Considering the toxicity of methanol and the safety,ethanol can be used as a carrier.The optimum extraction conditions of the crude oil extraction by supercritical CO₂ are:pressure 40 MPa,temperature 65 ℃,time 1 h,and liquid-solid ratio 1:1.The extraction rate is 18.7% under the optimum conditions.