During the process of oil-base drilling fluid in shale gas horizontal well，it is difficult to remove mud cake and oil film， leading to poor cementing quality and even sustained casing pressure. Based on the principle of micro-emulsion solubilization，a modified polyoxyethylene-polyoxylpropylene （PEO-PPO） block copolymer surfactant was prepared by using fatty alcohol， ethylene oxide and propylene oxide as raw materials. Then the oil displacement agent QX-1 was developed by the block copolymer surfactant and sodium dodecyl benzene sulfonate. The high efficiency oil displacement preflush fluid was prepared by mixing QX-1 with isolating agent GL-1，weighting agent barite powder with 23 μm（600 mesh）and water. The sedimentation stability，cleaning efficiency，interface bonding strength and compatibility of this prefluish fluid were evaluated，and it was applied on shale gas production layer cementing in Fuling area. The experiment results showed that the high efficiency oil displacement prefluish fluid had good sedimentation stability at 60—90 ℃ and excellent performance of cleaning efficiency. When the dosage of QX-1 was 20%，the cleaning efficiency at the simulated casing-cement interface was up to 93.94% and the mud cake removal efficiency at the cement-formation interface was 91.16%. And these two interfaces had reverse wetting properties after modified by high efficiency oil displacement preflush fluid，which effectively increased the interface bonding strength. Field application results showed that the compatibility of high efficiency oil displacement preflush fluid with oil-based drilling fluid and leading cement slurry in Fuling shale gas field was good. The cementing pass rate and the cementing quality rate was 100% and 92.73% respectively，which could improve the sustained casing pressure caused by poor interface cementing quality.