The invention relates to a purifying method of a novel antibiotic compound. The method includes: (1) a step of salifying, namely a step of adding cefazedone and sodium isooctoate into absolute methanol and performing a salifying reaction until the cefazedone is fully dissolved, with the temperature being controlled at 15-35 DEG C; (2) a step of decoloring, namely a step of adding active carbon into the reaction solution, stirring, decoloring, filtering to remove the active carbon, maintaining the temperature of the filtrate at 10-30 DEG C, and filtering again; (3) a step of crystallizing, namely a step of adding a certain amount of acetone and ethyl acetate into the filtrate after the filtration, controlling the temperature at 15-20 DEG C, growing the grain for 1-2 h, then adding a certain amount of the acetone and the ethyl acetate, stirring for crystallization with the stirring speed being maintained at 80-120 r/min, controlling the temperature at 15-25 DEG C, and growing the grain for 2-4 h; and (4) a step of drying, namely a step of filtering, washing the filter cake, and drying to obtain a purified product of the cefazedone sodium. Compared with the prior art, the method has characteristics of simple operation, low cost, high yield, and largely reduced pollution. The purified product of the cefazedone sodium has characteristics of low water content, low purity content and high stability.