Many approximately horizontal slip surface landslides are found in Jurassic red strata in Wanzhou of the Three Gorges Reservoir area. However，the formation mechanism of these landslides is not clear. In order to discover the causes of these landslides，experiments on rheological behaviors were performed on the sandstone of Erchengyan landslide bedrock in Wanzhou with triaxial creep test machine RLM–2000. Before the specimen failure，there is an accelerated creep stage，which lasts for about 8 h；this course is similar to the failure of deformation of some approximately horizontal slip surface landslides. Tautochrone of test data indicates this kind of rock is close to linear viscoelasto-plastic materials. Burgers model is used to fit the curves；and the three-dimensional constitutive relationship of Burgers model and its parameters are obtained. The results show that the proposed rheological Burgers model can exactly express the rheological characteristics of Jurassic red strata in Wanzhou. It can also describe the mechanism of the approximately horizontal slip surface landslides occurring in Jurassic red strata in Wanzhou. There is a nearly linear relationship between the creep strain rate and time in the beginning of accelerative creep stage. And the creep strain rate behaves closely to exponential growth with time in the last stage of accelerative creep. The accelerative creep shows highly nonlinear characteristics；and the creep strain rate displays a discontinuous form，which occurs in jumps change. Furthermore，the experimental results reveal the long-term strength of the rock is only 44 percent of the peak strength in triaxial tests. This conclusion is very helpful for the research on the mechanism and prevention of the horizontal slip surface landslides.