In order to study the damage evolution characteristics of sandstone with different moisture contents, uniaxial compression acoustic and electrical signal monitoring test was carried out for red sandstone under dry, natural and saturated conditions by using RMT-150C rock mechanics testing machine, AEwin-USB acoustic emission signal acquisition system and KBD5 electromagnetic radiation acquisition system. Based on the acoustic emission bell count, electromagnetic radiation pulse number and stress change during rock failure, the damage evolution model of sandstone is established. The results show that the characteristic curves of acoustic emission, electromagnetic radiation and damage variables are in good agreement with the stress-strain curves of rock. The damage evolution of sandstone can be divided into three stages: initial damage stage, continuous damage growth stage and rapid damage growth stage. As the damage degree deepens, the number of rings and pulses increases. In the stage of initial damage and continuous damage growth, the ratio of ringing count and pulse number in the saturated rock sample in this stage is the highest, followed by that in the natural state and the lowest in the dry state, while it is the opposite in the stage of rapid damage growth.