Abstract: In order to analyze the displacement mechanism of residual oil film in micro-channels, taking micro-channel residual oil film as an example, the paper analyzes the resistance acting on the residual oil film by rock wall, the interfacial tension between displacement fluid and residual oil film and the horizontal force on the residual oil film by displacement fluid after residual oil film wetting hysteresis occurring, and discusses the displacement mechanism of the residual oil film. Combined with continuity equation, motion equation and constitutive equations of visco-elastic fluid, numerical simulation is carried out to calculate the distribution of the horizontal stress acting on the residual oil film by displacement fluid with different rheological properties. The results show that increasing the horizontal force acting on the oil film can activiate the oil film to become movable oil; under the condition that the flow rate of the displacement fluid is constant, and the size and direction of the horizontal stress acting on the oil film by visco-elastic fluid will change. The existence of the elasticity can change the force distribution rules acting on the residual oil film and is in favor of the oil film activation