Abstract: Aiming at the issue of poor low-temperature fluidity of crude oil, which restricts the transport efficiency, in BY Oilfield, a novel composite copolymer pour point depressant GCJN-B(with primary agent GCJN-2) was prepared through screening of the primary agents and optimization of blending ratio. In view of such natures as high resin asphaltene and high wax content of crude oil in this oilfield, hydrocarbon sulfonate-fumarate copolymers(GCJN-1), polymethacrylate(GCJN-2), and polythene-vinyl acetate copolymer(GCJN-3) were selected as primary agents, with diesel oil as a diluent. Laboratory evaluations demonstrate that the pour point of crude oil dropped to 17 ℃ from 48 ℃ at a dosing concentration of 0.3% and a primary agent to diluent volume ratio of 1∶5. The viscosity of crude oil decreased from 448.7 mPa·s to 81.52 mPa·s at 50 ℃, with viscosity reduction rate of 82%. The micropolariscope observed that the microscopic morphology of crude oil wax crystals changed from large flaky aggregates to small particle point dispersions after adding the depressant, which increased the specific surface area of wax crystals, thereby, effectively inhibiting the formation of 3D network architecture, which improves the low-temperature fluidity of crude oil. On-site evaluations indicate that the optimum dosing effect of the depressant occurs at 55°C at least, reducing the wall loss from 9.4 to 0.6 tons per truck during crude oil transportation in winter. This pour point depressant provides a feasible solution for the efficient gathering and transportation of highly condensable crude oil.