Abstract: In water-rich mines or under water-rich mining conditions, the mechanical properties of coal-rock masses deteriorate significantly under environments with different water immersion depths, which jeopardizes the safety and stability of coal and rock system. In order to investigate the mechanical properties and damage characteristics of coal and rock under different immersion depths, typical coal, sandstone and shale were taken as research objects, and axial compression and acoustic emission tests were carried out at six different immersion depths of 0, 20, 40, 60, 80, and 100 mm to analyze their mechanical damage and instability mechanisms. The results show that: (1) With the increase of immersion depth, the elastic modulus, damage stress and compressive strength of coal rock decrease gradually, and the deterioration degree of elastic modulus and compressive strength of coal rock increases significantly, and the deterioration effect is the largest in the stage of 0−20 mm immersion. (2) With the increase of immersion depth, the cumulative ringing count and peak ringing count of acoustic emission decreased gradually. The cumulative energy is gradually reduced by the depth of immersion. (3) Based on acoustic emission RA-AF, Tensile cracks and shear cracks coexist in sandstone samples with different immersion depths. With the increase of immersion depth, the proportion of tensile cracks increases gradually, and the proportion of shear cracks decreases gradually. (4) Based on acoustic emission, the damage evolution model of coal rock is constructed, and the rationality of the damage model is verified from three aspects: stress-strain curve, damage effect and compressive strength. The damage evolution process of coal rock can be divided into the initial stage of damage, the stage of damage development and the stage of damage acceleration. With the increase of immersion depth, the damage variable of coal rock increases. (5) The multi-scale instability and failure mechanism of soaked coal rock is clarified from the "micro-meso-macro perspective". Under the action of soaking, the mineral particles inside the coal rock are dissolved, and the volume of the mineral particles decreases. Under the action of load, the mineral particles undergo micro-fracture, large-scale fracture, and full-fracture. New cracks are generated inside the coal rock and expand and penetrate. Cracks appear macroscopically, and the coal rock is unstable and destroyed. This research can provide useful reference for the safety, stability, prevention and evaluation of project coal and rock mass under the influence of immersion depth.