Acoustic test method and process are discussed in this paper. Through the speed of propagation of acoustic wave in rock mass, the authors established the mathematical model for the thickness of cracking rock mass and the degree of degradation. The results show that, where the thickness of cracking rock mass is less than 30 mm, the strength loss is relatively big; where the thickness of cracking rock mass is greater than 30mm, the strength is essentially unchanged. These data provide reliable scientific theoretical basis for the protection of Huashan rock paintings in the future.