Aiming at the problem of insufficient toughness of one-part geopolymer, three kinds of fibers, polyvinyl alcohol fiber, imitation steel fiber and calcium carbonate whisker, were selected to design the composition of single-doped and mixed-doped geopolymers. The effects of three kinds of fibers on the fluidity and mechanical properties of geopolymers were analyzed. Combined with scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, the mechanisms and patterns of fibers influence on the properties of geopolymers were investigated. The results show that all kinds of fibers reduce the fluidity of geopolymer to varying degrees. When the volume content of polyvinyl alcohol fiber, imitation steel fiber and calcium carbonate whisker is 0.6%, 1.5% and 1.5%, the fluidity of three kinds of single fiber geopolymer is 54.0%, 33.4% and 19.8% lower than that of the reference group, respectively. The incorporation of polyvinyl alcohol fiber and imitation steel fiber has a negative effect on the compressive strength of geopolymer, while calcium carbonate whisker shows a reinforcing effect. When the volume content of polyvinyl alcohol fiber, imitation steel fiber and calcium carbonate whisker is 0.4%, 1.2% and 1.2%, the flexural strength of hybrid fiber geopolymer increases by 89.1%. Microscopic analysis indicates that polyvinyl alcohol fiber enhances the toughness of geopolymers via bridging effects, imitation steel fiber contributes to toughening primarily through slip mechanisms, and calcium carbonate whisker improves flexural strength by filling voids. Optimized fiber proportion results in hybrid fiber geopolymers with superior fluidity and flexural strength.