The samples of layered rock mass with soft interlayers were made according to the geological structure of a hydropower project, and the triaxial rheological mechanics test was carried out under the action of seepage pressure by the automatic triaxial rheological servo system. The rheological properties and accelerated rheological properties of layered rock mass with soft interlayers are studied in this work. The long-term strength of rock mass is obtained according to the steady rheological rate of rock mass under different stress levels. It can provide reference for parameter identification of engineering rheological numerical tests of rock mass. According to the structural characteristics of layered rock mass with soft interlayers, a rheological model for the layered rock mass is proposed, which can reflect the rheological properties of layered composite rock mass. By introducing damage variables into the model, the rheological model can accurately reflect the rheological deformation characteristics of layered rock mass under different stress levels. Thereafter, the parameters of the proposed nonlinear damage rheological model were identified by the rheological test curve. The fitting curve fits well with the rheological test results, which verifies the applicability of the nonlinear damage rheological model to the layered rock mass.