The invention discloses a solvent method high-wet-modulus bamboo fiber and a preparation method thereof. The preparation method of the bamboo fiber comprises the following steps: activation, adding bamboo pulp into deionized water, adjusting the pH value, adding cellulase for activation, and then adding alkali to adjust the pH value; squeezing, vacuum dewatering and squeezing; pre-dissolving, adding water solution containing 50-88% of N-methyl morpholine-N-oxide; dissolving, entering a dissolving machine, heating, vacuumizing, dehydrating, dissolving, homogenizing and defoaming; spinning, spraying through a spinneret plate, and molding by adopting a dry wet spinning; washing; whitening; oiling; and drying. The preparation method has simple operation, no industrial pollution, low energy consumption and high safety performance, and is applicable to manufacturing the solvent method bamboo fiber by large-scale industrialized continuous production; furthermore, the bamboo fiber prepared by the method not only maintains the natural physical and chemical properties of the bamboo fiber, but also generates no harmful chemical residue and has higher wet modulus.