The invention discloses a preparation device for fibers and relates to the technical field of non-woven cloth spinning. The device includes a material hopper, a high-temperature screw rod, a distribution cavity, an air flow generator, an air flow heater, spinneret orifices and an alternative air flow generator; the material hopper is arranged above one end of the high-temperature screw rod, and the other end of the high-temperature screw rod is connected with the distribution cavity; the air flow generator is provided with the air flow heater; the spinneret orifices are formed in the lower endof the distribution cavity; two ventilation pipes are arranged at the lower end of the air flow generator; the material hopper is communicated with the spinneret orifices in the distribution cavity through the high-temperature screw rod; the alternative air flow generator is used for converting air flow generated by the air flow generator into alternative air flow and consists of a left air spraying pipe, a right air spraying pipe, a connecting shaft, a supporting shaft, a spring, a fixing shaft, a rotating shaft, a cam rotor, a power device and a column. The preparation device can improve the drafting efficiency and prepare thinner superfine fibers and is suitable for application in medical materials, filtering and adsorption materials and other domains.