To enhance the engineering durability of the loess in various environments, this paper employed biopolymer combined fiber to treat the loess, conducted unconfined compressive tests, and explored the compressive strength of biopolymers combined with fiber-treated loess as well as its variation rule and action mechanism under the influence of drying-wetting cycles and freezing-thawing cycles. The results indicate that, in comparison to untreated loess, the compressive strength and ductility of loess are markedly enhanced when biopolymer and fiber are incorporated. Specifically, when the mixture contains 2.0% (mass fraction) biopolymer and 1.00% (mass fraction) fiber, the compressive strength of the treated loess attains its peak value of 6.47 MPa. Under drying-wetting cycles and freezing-thawing cycles, the compressive strength of both treated loess and untreated loess decrease with the increase in the number of cycles. Nevertheless, after 10 drying-wetting cycles, the compressive strength of the treated loess is 7.40 times that of the untreated loess, and after 10 freezing-thawing cycles, the compressive strength of the treated loess is 2.30 times that of the untreated loess. In summary, biopolymers combined with fiber-treated loess can effectively enhance the engineering durability of loess in drying-wetting and freezing-thawing environments.