Abstract: According to the characteristics of mixed crude oil transported through Dongying-Xindian Oil Pipeline in gel and asphaltene content and wax crystalline distribution, BEM-JN series oil-based viscosity depressant is prepared, which is consisted of polymer and surfactant as main components. The main effective component is nonpolar-polymer, which functions on the wax, while the strong-polar-polymer functions on the gel and asphaltene. The reduction of crude oil viscosity is the result of these two kinds of comprehensive effects. The viscosity reduction effects under different heat treatment temperature by BEM-JN and BEM-3 are studied, respectively. The results show that higher heat treatment temperature is helpful to enhance the viscosity reduction effect for the two chemicals, while lower treatment temperature and higher test temperature will lead to tackify. The indoor and field experiments show that BEM-JN has good performance in the light of the crude oil in Dongying-Xindian Oil Pipeline, and can meet the demands in safe running under low throughput for the pipeline.