The invention relates to a multi-purpose gelatin fiber and a preparation method thereof, in particular to the preparation of amphipathy polymer and emulsion thereof, the preparation of spinning solution, fiber spinning, after-treating of the fiber and the like, wherein firstly free radical polymerization or polyurethane prepolymer is adopted for compounding amphipathy polymer which is prepared into emulsion in water, and then the emulsion is added into a gelatin solution to prepare spinning solution with certain viscosity; the spinning solution is prepared in to fiber by a wet spinning; and finally in order to increase the intensity of the fiber, the fiber is needed to be post-treated. The gelatin fiber and the preparation method thereof belong to the textile industry technical field; andthe formed fiber can be used for clothing material, biology medical material and hairpiece products.