Abstract: The failure of rock engineering, including tunnels and slopes etc.,generally experience progressive damage by time-dependent behavior of rock mass. In this paper, the stavrite from a dam foundation were studied, and two groups of stepwise stress uniaxial relaxation tests were conducted. The stress relaxation behaviors as well as its stress relaxation rate under different stress conditions were analyzed. Test results showed that the stress relaxation could be divided into three stages:rapid relaxation stage, deceleration relaxation stage and stable stress stage, and stress relaxation behaviors are closely related to the cracking behaviors and viscous deformation. Finally, a nonlinear Maxwell model was proposed to describe stress relaxation behaviors, fitting results using this nonlinear Maxwell model present a good agreement with test results.