The invention belongs to the technical field of mechanical performance test, and relates to a test clamp suitable for high-temperature lasting creep deformation of a plate-like test sample. The clamp comprises two portions, namely, a clamp main body and a cushion block assembly, wherein the clamp main body is a cuboid shaped like the Chinese character Hui, a cavity is formed in the clamp main body, the cushion block assembly is divided into two elements, and longitudinal axes of the clamp main body, the cushion block assembly and the plate-like test sample stay on a same straight line; and the plate-like test sample is installed and clamped, a parallel section of the plate-like test sample is arranged between the two elements and fixed together by virtue of bolts, and then the test sample is integrally placed into the cavity of the clamp main body. The test sample and the clamp are connected in a clamping end suspension manner, so that the defect that a clamped end of the test sample is broken due to the pin connection can be overcome, the test failure probability is reduced, and the problems such as data inaccuracy, resource waste and the like can be avoided. The structure of the test sample is not only suitable for the high-temperature lasting and creep deformation of the plate-like test sample, but also suitable for testing mechanical performances of the plate-like test sample such as single-shaft tensile at a room temperature and high temperature, tensile fatigue and the like.