The invention relates to a porous silk fiber material and a preparation method thereof. The preparation method includes the following steps that 1, silk is put in an acid solvent to fully swell; 2, a silk sample obtained after swelling is put in the environment of the temperature below the freezing point of a swelling solvent for freezing treatment; 3, the frozen silk is put in an organic solvent or water to be soaked for removal of the swelling solvent; 4, the treated silk is freeze-dried, and the porous silk fiber is obtained. The porous silk fiber is prepared through the method, equipment and the process are simple, fewer operating influence factors exist, control is promoted, and the porous silk fiber is suitable for experimental study and mass production; according to the prepared porous silk fiber, the specific area and porosity of the silk are greatly increased, the silk fiber density is reduced, and the product can be used for the novel technical fields of tissue engineering, air filtering, medicine slow release and the like.