To clarify the effects of chemical corrosion and high temperature on mechanical properties of sandstone, the uniaxial compression and three-point bending tests were carried out on sandstone samples that were immersed respectively in water, HCl, NaOH solutions and then suffered to high temperature treatment. The damage mechanism was analyzed by the patterns from scanning electron microscope and X-ray diffraction. The experimental results show that the uniaxial compressive strength of sandstone after immersed in NaOH solution and high temperature treatments is obviously improved, but deteriorates gradually when the temperature is below 400℃ for that immersed in HCl solution and water. The fracture toughness of sandstone after immersed in NaOH solution decreases by 16.05%. As the temperature increases, the fracture toughness and tensile strength decrease generally. As a result, 400℃ is the threshold temperature of deterioration of fracture toughness and tensile strength. The internal mineral composition, crystallinity and structural integrity of sandstone are changed after chemical corrosion and high temperature treatment, which affects the mechanical properties of sandstone.