Microporous silicon carbide fiber and method for preparing same. The microporous silicon carbide fiber is characterized in that the Si content is 40-65wt%, the C content is 25-45wt%, and the balance is O, in the form of continuous fibers, and the volume of micropores (pore diameter≤2nm) accounts for 85vol% of the total pore volume Above, the average pore diameter is 1.30-2.00nm, and the specific surface area is 1100-2100m2 / g. The preparation method is characterized in that the C-rich silicon carbide fiber is firstly prepared by polycarbosilane and carbonaceous polymer blend spinning, non-melting, and cracking, and then the microporous silicon carbide fiber is obtained by activating the C removal process. The microporous silicon carbide fiber of the present invention has high micropore volume content, stable pore size, is not easy to collapse, high specific surface area, high temperature resistance, good oxidation resistance, and has good applications in the fields of environmental management, energy storage, medicine and health, etc. prospect.