The utility model provides a tool bit clamp and a tool bit pressing mechanism thereof and belongs to the field of operating technology. The tool bit clamp and the tool bit pressing mechanism thereof solve the problem that existing workpiece clamps cannot clamp thin tool bits stably to result in extrusion deformation. According to the tool bit pressing mechanism of the tool bit clamp, the tool bit clamp comprises a base, and the tool bit pressing mechanism is characterized by comprising a left pressing block and a right pressing block; two pressing air cylinders are fixed onto the base, the piston rod of one of the pressing air cylinder is fixedly connected with the left pressing block, and the piston rod of the other pressing air cylinder is fixedly connected with the right pressing block. When applied to clamping tool bits, the tool bit pressing mechanism and the tool bit clamp have the advantages of being firm and stable in clamping and less prone to leading to deformation of the tool bits, thereby being particularly applicable to clamping thin tool bits. The tool bit clamp also has the advantages of being convenient to adjust, long in service life and capable of improving the tool bit grinding efficiency of a grinding device.