In order to have a better understanding of the mechanism of oil film displacement，the oil film displacement experiments are conducted. Considering the effects of emulsifying speed and emulsification amount，the emulsification index（EI）is used to quantitatively characterize the emulsification capability of the chemical flooding agents. For the low and medium viscosity oil used in experiments，three kinds of oil displacement agents are screened，which have the strong emulsification capability and ultra-low interfacial tension（IFT），strong emulsification capability and low IFT，and weak emulsification capability and ultra-low IFT，respectively. And then，the three kinds of oil displacement agents are used to conduct the oil film displacement experiments based on the glass rod bundle model. For the low viscosity crude oil，the oil film displacement efficiencies of the oil displacement agents with higher emulsification capability（EI are 0.667 and 0.706 respectively）are about 90% no matter the IFT of displacement agents is ultra-low，while the oil film displacement efficiency of the oil displacement agent with weak emulsification capability and ultra-low IFT（EI=0.244）is less than 70%. For the medium viscosity oil，the oil film displacement efficiencies of the oil displacement agents with higher emulsification capability（EI are 0.534 and 0.602 respectively）are about 83% no matter the IFT of oil displacement agents is ultra-low，while the oil film displacement efficiency of oil displacement agent with weak emulsification capability and ultra-low IFT（EI=0.258）is less than 65%. The research results show that the oil film displacement efficiencies mainly depend on the emulsification capability of the oil displacement agents.