Creep is a common rheological behavior of surrounding rock in rock engineering, especially under the action of seepage water pressure, which poses a serious threat to the safety and service life of the project, so it is very important to maintain the long-term stability of the project. Creep tests under different hydraulic gradients were carried out by using seepage-stress coupling servo control loading system to explore the creep characteristics and seepage characteristics of sandstone. Combined with 3D digital image correlation technology (3D-DIC), the evolution law and deformation localization characteristics of micro-cracks in sandstone were studied. At the same time, the crack damage characteristics of sandstone were explored based on CT scanning technology. The test results show that: (1) The greater the hydraulic gradient, the greater the creep deformation, the faster the growth rate of micro-cracks, and the more obvious the change of strain field nephogram. Compared with the axial strain field, the larger strain point and strain localization appeared earlier in the radial strain field nephogram. (2) The greater the hydraulic gradient, the greater the strain increment, the faster the strain change rate and the shorter the creep life of sandstone. By establishing virtual strain gauges, it was found that the strain changes inside and outside the failure zone were inconsistent, indicating that there was localization in the creep deformation process of sandstone. (3) Under the low hydraulic gradient, the pores and fractures were more tightly closed, the seepage channels were reduced, and the flow rate was decreasing. Under the high hydraulic gradient, the damage was accumulating, the seepage channels were increasing and the flow rate was increasing. (4). It could be observed in the CT scan that the main crack ran through the whole specimen, which led to the failure of sandstone, and at the same time generates secondary cracks and promoted the crack propagation. Near the end with higher seepage pressure, there were more secondary cracks in sandstone, forming a complex crack network structure.