PURPOSE: Ultrafine alumina powder castable without having cement is provided for more strength than an existing castable by using an electrostatic interaction of ultrafine alumina powder as a binder at low temperature and high temperature, and for abrasion resistance, erosion resistance, explosion resistance and less contraction. CONSTITUTION: Ultrafine alumina powder castable without having cement comprises 30-45 wt.% of alumina having 3-10mm of a particle size; 9-20 wt.% of alumina having 1-5mm of a particle size; 15-27 wt.% of alumina having 1-0.074mm of a particle size; 5-15 wt.% of alumina having 150-250 mesh of a particle size; 5-17 wt.% of alumina having 200-400 mesh of a particle size; 5-15 wt.% of ultrafine alumina having 500-1,500 mesh of a particle size; and 1-10 wt.% of inorganic binder having 150-250 mesh of a particle size, less than 40 wt.% of silica sand and higher than 60 wt.% of alumina. Moreover, the ultrafine alumina powder castable adds one more compound from silica fiber or steel fiber.