The invention discloses a method for spheroidizing a hexanitrohexaazaisowurtzitane (HNIW) explosive. The method comprises the following steps: I. adding explosive crystals into an etching liquid, heating to a certain temperature, mechanically agitating for certain time, and then filtering and washing the explosive; II. adding the explosive in the step I. into a surface polishing solvent, mechanically agitating at normal temperature, then filtering and washing materials, and drying to obtain the spherodized explosive crystals. The method is applicable to spheroidization of CL-20 crystals with various particle size and various crystal forms, is simple in technological flow, mild in reaction conditions, good in reproductivity, high in yield, and applicable to industrial batch production; the prepared spheroidized CL-20 explosive crystal product is approximately spherical, has less edges and smooth surfaces; the internal defects of the particle crystals are fewer, the open-setting stacking density is high, and the mechanical sensitivity is obviously reduced.