The invention discloses porous magnesium salt nanofiber synthesized from magnesium-based amorphous alloys and a preparation method of the nanofiber. By use of the characteristics that amorphous alloyshave ingredient and structure uniformity and controllable corrosion degradation rate, the magnesium-based amorphous alloys with good biocompatibility are taken as raw materials and subjected to a corrosion degradation reaction in a PBS solution of a simulated body fluid under the conditions of room temperature, normal pressure and no catalyst with a simple solution soaking method, the porous magnesium salt nanofiber is synthesized, the nanofiber material is rapidly and directly synthesized from blocky amorphous materials, and the defects that existing magnesium salt nanofiber synthesis methods are complicated, high in production cost and not favorable for large-scale production are overcome. The magnesium salt nanofiber has a large number of nanoscale holes and can be dissolved again after being soaked in the simulated body fluid. Therefore, the porous magnesium salt nanofiber can be used as a drug sustained release carrier material and has good application prospects in the field of biological medical materials.