The micro-stress assembling technique for the main reflector component of a space remote sensor was discussed. The reflector component was assembled when it had the surface deformation of λ/10 (λ=632.8 nm). To reduce the influence of the assembling stress on the reflector surface accuracy to the greatest extent, the stress of the main reflector was analyzed and the assembling process and adjustment device were designed. After the reflector was assembled, none changes of its surface deformation were measured. Finally, the reflector was verified in both mechanical test and vacuum thermal cycling test. The result showed that this assembling technique met the design and operation requirements.