The creep of the red layer side slope is remarkable, and the rock has strong creep characteristics. In order to reflect the whole process of the rock creep, the elastic strain, the viscoelastic strain and the viscoplastic strain of the rock creep were respectively described by the elastic body, the soft element based on the fractional calculus and the viscoplastic body based on the phase characteristic of the rock creep. The damage variable was added to the elastomer, the SN element was introduced to improve the fractional-order soft element, the modified elastomer and the non-unsteady viscous body and the viscoplastic body based on the fractional calculus were integrated, and a new constitutive model of the three-element creep damage was constructed. The triaxial compression and creep test of red-layer mudstone is carried out by the RLW-2000 three-axis rheological test system, and the typical creep data of the red and red sandstone in the relevant literature are cited, and the model is verified by three kinds of rock creep curves, and the rationality and applicability of the model are proved.