Phase change polymer is a new type of oil displacement agent that triggers the transition of gel into solution through temperature response fracture of ester crosslinking agent. This article investigates the phase change performance, rheological properties, and shear resistance. The results show that compared with conventional polymers, phase change polymers undergo a phase change process of “gel phase-coexistence phase-solution phase”. The “gel phase” elastic modulus is 6.9 Pa, the shear resistance is stronger, and the shear viscosity loss rate is 14.1%; The elastic modulus of the “coexistence phase” gradually decreases, and the apparent viscosity gradually increases, showing a time-varying trend; The “solution phase” relies on the hydrolysis products of ester crosslinking agents to enhance intermolecular forces, with stronger thickening ability, the apparent viscosity is 49.1 mPa·s. Using core samples and visualization models, the seepage flow characteristics, displacement mechanism, and residual oil recovery capacity of phase change polymers are studied. The results show that high strength plugging can be formed after “gel phase” swelling, which can trigger the diversion of liquid flow; After semi dissolution, the “coexistence phase” can temporarily block migration and prolong the depth of displacement control; The “solution phase” can control the fluidity, further expand the swept volume, and has a three-stage oil displacement mechanism. Under heterogeneous conditions, the recovery rate is increased by 29.0%, which is higher than the 20.3% of conventional polymers. The phase change polymer was tested in the Bohai 76 block of the Gudao oilfield, and since its injection, the oil pressure has increased by 1.67 MPa, the water content has decreased by 5.72%, and the effect of water cut and oil production is good, indicating the feasibility of technical promotion.