Abstract: The variation of formation water content has a great influence on the creep characteristics of mudstone reservoir, especially in the process of injection and production casing deformation in mudstone section can lead to casing damage. In this paper, a water-cut element was added on the basis of Burgers model to improve the accuracy of the instantaneous creep stage model. At the same time, a comparison was made on a mudstone block in an actual oil field. It was concluded that with the increase of water-cut, the formation creep variable increased and the time of the instantaneous creep stage decreased. At the same time, the thickness of casing wall, elastic modulus of cement ring and water content of formation can greatly affect the casing deformation under creep condition, while the casing size has almost no effect on the casing deformation. The research results can more accurately calculate the casing deformation of mudstone creep under different water content conditions, and effectively prevent and control the wellbore damage.