There are various stress states of solid waste mass in landfills (e.g., compression, tension, loading, and unloading), which are difficult to be fully simulated by using conventional triaxial tests and direct shear tests. Triaxial tests on reconstituted municipal solid waste (MSW) specimens under nine stress paths were carried out by GDS triaxial apparatus to analyze the influence of stress path on the stress-strain behavior and yielding characteristics of MSW. A unified mathematical model was proposed to describe the stress-stain responses of MSW, and the yielding locus of MSW was obtained in p-q stress space. By comparing the stress-strain relationships of sand soil and MSW, the effects of stress path on the reinforcement of fiber materials in MSW were discussed. Results show that for compression stress path with σ₃≥0, the stress-strain curves of MSW exhibited an upward curvature without any peak or asymptotic values, and the reinforcing effect of fiber materials was the most significant. For compression stress path with σ₃<0, the deviatoric stress of MSW increased with increasing axial strain and it gradually tended to a certain value, while the fibrous reinforcement was weak. For extension stress path with Δq<0, the stress-strain relationships of MSW were almost the same as those of sand soil, and there was no fibrous reinforcing effect in MSW. In conclusion, the fibrous reinforcing effect in MSW is closely related to stress path, and the research data provides a basis for comprehensive and in-depth understanding of the mechanical properties of MSW.