In order to investigate the influence of pore water pressure on the short-term creep properties of weakly altered granite, short-term creep tests were carried out under triaxial graded loading, systematically studying the short-term creep mechanical behavior and creep constitutive model under the combined action of pore water pressure and high confining pressure. Test results show that: (1) Under pore water pressure, the degradation trend of rock mechanical properties is obvious; the peak strength and elastic modulus of rock samples attenuated by 23.59% and 19.43%, respectively, as pore water pressure increased from 0 MPa to 4 MPa; (2)The creep process exhibits two-stage characteristics: decay creep and steady-state creep. At high pore water pressure, the decay creep stage is extended, while the steady-state creep rate increases. The creep stiffness decreases nonlinearly with increasing time and pore water pressure. (3) With the increase of pore water pressure, the failure pattern of rock samples evolves from single shear cracks into multi-fracture V-type cracks, and secondary cracks propagate and coalesce; (4) Based on the Burgers model, a pore water pressure degradation coefficient and a time-dependent damage equation were introduced, constructing a three-dimensional nonlinear creep constitutive equation. The model parameter identification results show good agreement with the experimental data. The results of this research can provide a reference for the stability control of reservoir bank slopes.