Abstract: A clamp and a shear test device are provided, and relate to the technical field of rock mass mechanics tests. The clamp comprises a box body, wherein an opening is formed in one side of the box body, two clamping structures are oppositely arranged in the box body, a sample is arranged between the two clamping structures, each clamping structure comprises an adjusting mechanism, and a distance between the two clamping structures is adjusted through adjusting mechanisms of the two clamping structures. According to the clamp, real-time dynamic adjustment is conveniently and rapidly achieved, the stability of sample clamping is ensured, and therefore the requirement that the shear load can be truly and effectively transmitted to the sample through the box body is met.