The invention relates to an optical tool regulator for an excimer laser micromachining system, which belongs to the technical field of micro-nanoscale science and is used for MEMS machining. In the optical tool regulator, a sliding seat (1) is arranged on an optical guide rail; a regulating seat (2), a supporting plate (3), a mirror bracket (4) and a tight positioner (5) are sequentially arrangedon the sliding seat (1); the mirror bracket (4) is provided with an optical tool hole (22) capable of accommodating a circular optical element with heavy caliber; and a square optical element regulator (23) arranged in the optical tool hole (22) and a light-reflecting inclined frame seat (32) capable of converting light paths are arranged. The optical tool regulator can realize five-dimensional fine adjustment in the X direction, Y direction, Z direction, pitching direction and the direction of left and right rotation, and also can convert the light paths by 90 degrees and is provided with square optical elements. The tight positioner (5) is directly connected with the regulating seat (2), and coats the periphery of the mirror bracket (4), a plurality of screw holes are uniformly formed at the periphery of the lateral surface of the tight positioner, and the tight positioner butts against the mirror bracket (4) fixedly through bolts, so that the optical elements work reliably and stably for a long time.