During the hydraulic structure design, the stability of abutment slope is critical to the normal operation of hydraulic structure. Through the tests, the effects of different hydraulic pressure on the strength and deformation characteristics of sandstone were studied, and the variation characteristics of rock masses with joints under secondary loading after excavation damage were analyzed as well. Test results show that: 1. When the samples without immersion secondly load until complete failure, ultimate strain increases slightly than the first loading, of which the increasing value is 7.5%; elastic modulus has a relatively large reduction than the first, which reduces 22.8%; deformation modulus has a less reduction, which is about 3.3%; 2. When considering the softening action of different hydraulic pressure on samples, ultimate strain increases by about 23% than that without consideration of immersion effect; elastic modulus reduces about 53%; deformation modulus reduces about 39%; 3. With the increment of immersion pressure, sample strength decreases greater, so does the softening effect of water on rock samples. With the increment of pressure, the strength of rock with joints has a relatively large reduction, which is from 27% to 41%, and the increasing value of intact rock mass isn't great, which is only from 25% to 27%. Jointed rock masses are more sensitive to the softening effect of water, and mechanical properties weaken obviously after long-term immersion with unstable problem.