Abstract: The affecting mechanism of new amphoteric betaine surfactant on residual oil in dead-end,prismatic residual oil and residual oil film on the wall of channel after water flooding was experimentally studied by micro model for oil displacement.The displacement and migration process and mechanisms of those residual oils were analyzed.The effects of the new amphoteric betaine surfactant on residual oil and the possibility for enhancing oil-displacement efficiency after polymer flooding were studied.The microscopic oil-displacement mechanism of surfactant solution could be perfected.The study shows that enhancing oil-displacement efficiency by surfactant was controlled by the effects of ultra-low interfacial tension and the inversion of wettability.