The invention discloses a positioning and protecting device for polishing of a light guide plate. The positioning and protecting device comprises a machining base, lifting motors, supporting columns, a machining platform, rectangular press plates, hinge seats and connecting rods. By arranging the rectangular press strips and fasting bolts, the light guide plate can be fixed and clamped conveniently, the situation that the side edge of the light guide plate warps or collapses during polishing is avoided, the machining quality of the light guide plate is improved, the multiple light guide plates can be polished at a time, and the polishing efficiency is high. By arranging the lifting motors and the supporting columns, the height of the machining platform can be adjusted by controlling a lifting control button on the machining platform, and workers with different heights can conduct polishing treatment conveniently through handheld equipment. By arranging first check blocks and second check blocks, the multiple light guide plates placed into the machining platform can be positioned in multiple directions, and the multiple light guide plates to be polished can be placed on the machining platform in order. The positioning and protecting device is simple in structure, convenient to operate, high in working efficiency and good in practicability.