Laser system requires that optical beam has excellent pointing stability after long optical path transmission, which is directly determined by the structural stability of optical mounts. In order to achieve beam pointing stability and alignment, optical mount is often required to have excellent structural stability and adjustability. Due to the existence of clearance fit, the adjustability will lead to instability. Aiming at the instability caused by grease in adjustment screw structure of the mount, a structure improvement design was proposed. Axial slots were machined on the internal thread surface of the nut in the adjustment structure. Combined with the proposed structure, a heat treatment process was further proposed, which can greatly reduce the instability introduced by grease. Change of axial clearance of two adjustment structures were tested. Structure stability of optical mount with slotted adjustment structure was compared with the un-slotted mount before and after heat treatment. The results show that the slotted adjustment structure after heat treatment can greatly improve the stability of optical mount.