The invention provides a high-precision flat plate-type brake test bench, which is composed of a supporting frame, a brake soleplate, a bearing frame, brake force detection mechanisms, a wheel weight detection mechanism and a guide limiting mechanism, wherein two sides of the supporting frame are symmetrically provided with two grooves, the notch of each groove faces inwardly, and thus, the supporting frame presents a symmetrical structure in a shape like a Chinese character zhong; the bearing frame is arranged at the inner side of the supporting frame; the brake soleplate is fixedly arranged above the bearing frame; two groups of brake force detection mechanisms are symmetrically arranged in the grooves at two sides of the supporting frame; the wheel weight detection mechanism is located between the bearing frame and the bottom plate of the supporting frame; and the guide limiting mechanism is connected with the bearing frame and the supporting frame. The technical scheme of the invention can effectively improve defects existing in aspects such as the overall frame structure of the traditional flat plate-type brake test bench and the wheel brake equivalent transfer and brake force acquisition, and the brake force detection precision of the flat plate-type brake test bench is improved.