The understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock engineering.Tensile strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying cycles.The crack propagation process and acoustic emission characteristics of the tested samples were obtained through a high-speed camera and acoustic emission system.The results indicate that the tensile strength is observably reduced after cyclic wetting-drying,and the extent of the reduction is not only related to the number of wetting-drying cycle,but also closely related to the clay mineral content of the sample.In addition,as the cycles of wetting-drying increase,the effect of each single cycle on tensile strength get reduced until it becomes constant.Moreover,the crack initiation and penetration time is prolonged as the number of wetting-drying cycle increases,which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of sandstone.Meanwhile,the acoustic emission characteristics of the tested samples further confirmed the ductile behaviour of the sandstone samples with increasing wetting-drying cycle.Furthermore,through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles,it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction,chemical and corrosive deterioration.