Abstract: Soft rocks have significant degradation effects when they encounter water. Previous studies focused mainly on the rheological properties of soft rocks. Water damage of soft rocks under water-rock reactions was seldom examined. The effects of water damage on soft rocks under water-rock reactions are important in the guidance of project constructions. Therefore, this article takes the silty mudstone in the central Yunnan area as the research object, and the triaxial compression creep test on the silty mudstone samples is performedunder dry conditions, natural water content and saturated water conditions. The test results show that (1) the strain of the samples with different water content during the initial loading stage is much larger than the strain increase in the later stage of the stage loading, and the initial loading creep variable gradually increases with the increasing water content. (2) As the water content increases, the final creep variable gradually increases, and the stress threshold of the sample entering the accelerated creep stage gradually decreases, but the long-term strength is significantly reduced. Based on the test results and the damage theory, a nonlinear viscoplastic body is introduced to consider the effect of water content on creep, and a water damage constitutive model based on the classic Burgers model with water-rock degradation characteristics is proposed. The parameters are identified by the 1stopt software, and the accuracy and adaptability of the model are also verified. The research results can provide a certain reference for the research on the water damage characteristics of the red rock in central Yunnan.