In order to meet the demand for demulsification in Xinjiang oilfields, and reduce the environmental pollution of common oilfield chemicals, this article based on environmental safety and the complex situation of shale oil fracturing produced fluids in the Madong block in Xinjiang, and fifteen kinds of biodemulsifiers synthesized by microbial fermentation were screened and evaluated by the bottle test method. The demulsification of the fermentation broth and the purified extract was compared, and the results showed that the biodemulsifier XJ-4-2 synthesized by the XJ-4 bacteria had good compatibility with the extracted fluid from the Madong block and more than 80% dehydration rate. In order to improve the demulsification efficiency and reduce the cost, a composite system of biological demulsifier and conventional chemical demulsifier is adopted. After optimization, the demulsification efficiency of the composite system of biological demulsifier XJ-4-2 and chemical polyether demulsifier reaches above 95％. Through the optimization of the dosing process, the initial water content is 43.76%. When the chemical demulsifier 200mg/L is added at 60 ℃, the dehydration rate after 2h sedimentation is 91.45%, the remaining water content ratio of crude oil was 8.43%, and the oil content ratio of sewage is 228mg/ L. The initial water content of the improved crude oil is 33.85%. At 50 ℃, when the compound formula 200mg/L is added, the dehydration rate after 2h sedimentation is 94.56%, the remaining water content ratio of crude oil 1.84%, and the oil content ratio of sewage is 156mg/L. In summary, the biological demulsifier has high dehydration rate at low temperature and low sewage oil content. It is of great significance for the efficient separation of produced fluids from fracturing exploitation of shale oil in the Madong block and ensuring the normal operation and economic benefits of the oilfield.