The high-precision focusing mechanism applied to space optical remote sensors belongs to the field of space remote sensing technology. In order to solve the problem that the existing focusing mechanism uses a link mechanism as a connecting part, the mechanism is complex and the focusing amount is nonlinear, and the focusing control and assembly are added. Difficulty problem, the driving part includes: motor, first coupling and worm; the actuator includes: encoder, second coupling, bearing seat, bearing, worm gear, Hall element, magnetic steel, lead screw, special-shaped nut, screw, linear bearing seat, linear bearing, sliding shaft, adapter seat, focusing lens assembly, linear guide pair and focusing base; the high-precision focusing mechanism uses a worm gear pair and a screw nut pair to realize the transmission relationship, The nut directly drives the focusing lens assembly to move horizontally, which has high focusing precision and can linearly control the focusing amount.