In order to study damage effect of AMD(Acid Mine Drainage) on mine slope,two kinds of H_2SO_4 solutions with pH value of 1.07 or 3.26 were used to corrode the sandstone samples at the condition of different time steps,then the compression strength of the corroded sandstone samples was tested,and their microstructure was obserxed.The results indicated that the uniaxial compression strength of the corroded sandstone decreased by 30%~50%,its elastic modulus dropped by 25%~45%,the cohesion and internal friction angle decreased also,its Poisson ratio fluctuated at the range of 0.20~0.29;the more the joints develop,the bigger the residual stress after the peak value,the longer the time to damage.The microstructure research showed that after sandstone was corroded by AMD,the elements contained in sandstone such as Fe,Al,etc,had been attenuated and dissolved,the mass percents of above elements had been greatly declined.The reaction mechanism analysis indicated that the joints inside the sandstone and the fillings between fissures frequently take place the decompose and polyreaction during the AMD corroding,it changes the molecular structure inside the rock mass and the composition of its framework,so reduce the cohesion and the internal friction angle of rock mass.