The invention discloses a method for preparing chitosan fibers, which comprises the following steps: mixing 2.0 to 6.0 weight percent of chitosan, 4.0 to 6.0 weight percent of lithium hydroxide, 0.5 to 4.0 weight percent of urea, 0.1 to 3.0 weight percent of glycerol and the balance of water, and swelling to prepare chitosan spinning solution; and spinning by a wet-process spinning method, coagulating and precipitating in a coagulating bath to form protofilaments, washing, drawing, and drying to obtain the chitosan fibers. In the invention, the spinning solution is prepared by dissolving chitosan in an alkaline solvent, the chitosan macromolecular chains exist in a high-swelling state, the arrangement of the chitosan macromolecular chains is more compact, the high instability of the chitosan in acidic solution is overcome, the hydrolysis of the chitosan macromolecular chains and the breakage of the glucosidic bonds are avoided, the oriented arrangement of the macromolecular chains is promoted, and the mechanical properties of the chitosan fibers are improved.