To systematically investigate the influence of fiber types and hybrid configurations on the mechanical properties of loess, this study conducted comparative reinforcement tests on Xining loess from Qinghai Province using basalt, polypropylene, and their hybrid fibers. Conventional triaxial tests were performed to determine the optimal dosage of single fibers and the optimal blending ratio of hybrid fibers for Xining loess. The mechanical and thermal properties of unreinforced loess and hybrid fiber-reinforced loess under varying water contents (i.e., 10%, 12%, 14%, 16%, and 18%) and freeze-thaw cycles were evaluated. Scanning electron microscopy was utilized to assess the reinforcement mechanism at the microstructural level. The research results indicate the following: (1) At a basalt-to-polypropylene ratio of 3∶2, hybrid fiber reinforcement improves the soil strength by 23.2% and 13.2% compared with basalt and polypropylene single-fiber reinforcement, respectively. (2) For hybrid fiber reinforced loess, cohesion and elastic modulus initially increase and then decrease with the increase in water content, peaking at a water content of 14% for maximum strength enhancement and best reinforcement effect; internal friction angle and thermal conductivity exhibit a decreasing trend with the increase in water content, although with smaller variations than unreinforced loess. (3) Under freeze-thaw cycles, cohesion, internal friction angle, elastic modulus, and thermal conductivity of the samples all show a decreasing trend. After 20 freeze-thaw cycles, the difference in strength loss rate between hybrid fiber-reinforced loess and unreinforced loess reaches a maximum of 9.8%. These results provide theoretical and practical references for the engineering design of hybrid fiber-reinforced soils.