Abstract: The variation rule of the microstructure and residual stress in linear guide under different thermal aging conditions was studied by means of scanning electron microscope（SEM）, X-ray diffractometer（XRD） and X-ray stress tester.The results show that with the increase of aging temperature and heat preservation time, the morphology characteristics of martensite body in the linear guide rail quenching layer are no longer obvious, part of the residual austenite decomposes, the content of carbides first increases in number then tends to be stable, and larger bar carbide appears. This leads to a small decrease in the hardness from the quenching layer to the core. The surface hardness decreases to 680.1 HV. During the aging process, the residual stress of linear guide is eliminated to different degrees, and the elimination rate of base level residual stress is up to 68.9%, and the deformation rate of guide rail is reduced by 64.5% compared with that before aging.