Abstract: Aimed at the degradation of the mechanical properties of the sandstone in the acid environment, the experiments of the feldspathic sandstone samples submerged in various acid solutions with different pH values are carried out. The mechanism of chemical reaction is also revealed with analyzing the results of compression test and CT scanning. The solution of the main cement of rock-CaCO3 is considered as the reason of the degradation of the strength and deformation properties of the rock. A strength model for chemical damage of rock in the acid solution is then established using theories of chemical kinetics and damage mechanics,and examined using the experiment results.