The soil water characteristic curves (SWCC) of municipal solid waste (MSW) samples with different compaction densities from the Jiangcungou landfill in Xi’an are tested in a laboratory. In addition, the Jiangcungou landfill was used to analyze the effect of different slope ratios, rainfall amounts and patterns, compaction degrees, and the leachate drainage system on stability of the landfill based on the saturated-unsaturated seepage theory and the Morgenstern-Price method. The results are summarized as follows. First, the SWCC of MSW samples with different compaction densities and the same components gradually converged with an increase in matric suction, and it nearly converged to one point when the matric suction was approximately 10⁴ kPa. The volumetric water content of the converge point was the greatest in the deep layer, followed by the middle and shallow layers. Second, for the MSW samples with the same compositions, in the range of dry densities tested, MSW samples with a large compaction density tended to have a small α, a saturated water content of θ_s and n_v, and little differences in the residual water content, θ_r. Third, for the compaction, drainage system, slope, and rainfall, the value of R (i.e., range) was 0.49, 0.22, 0.19, and 0.12, respectively, in the orthogonal test. Thus, the order of impact on the landfill is as follows: the compaction, drainage system, slope, and rainfall intensity.