A device for implementing a high-temperature plane strain compression test on a thermal simulation tester is provided. High-hardness and special-shaped pressure heads are located at the upper and lower ends of a sample; side shim plates and end shim plates with insulation and high pressure resistance are respectively located in grooves in the end faces and the inner sides of high-strength fixed plates, and the combined fixed plates are respectively located on the left and right sides of the sample; and the combined fixed plates are fixed via four through holes of the fixed plates by high-strength bolts, washers and nuts to limit the plane strain problem caused by the deformation of the sample in the normal direction of the fixed plates.