The utility model provides a waterstop restraining device includes: first positioning fixture, second positioning fixture, fixed platform, first positioning fixture is the L font, the second positioning fixture is the L font, it has the logical groove of two bars to open on the first positioning fixture, it has the logical groove of two bars to open on the second positioning fixture, last the opening of fixed platform has 4 fix with screw holes, first positioning fixture with the second positioning fixture passes through screw movably connected and is in fixed platform is last. The waterstop restraining device and waterstop slicer that this application provided, through having increased recess limit for width fixture device, control elastomer or the soft type of condition that the material caused not cut well because of the deformation that can be fine to the width can be controlled to these anchor clamps, can adjust according to the width of different materials, then sharply be cut into corresponding thickness, can reduce the test result influence through this kind of thickness adjustment mode.