The invention discloses a preparation method of a cefminox sodium powder-needle preparation for injection, and belongs to the technical field of biomedical synthesis. The method comprises: mixing the prepared raw materials, respectively carrying out an acylation reaction and a carboxyl protection removing reaction, treating the solution obtained after the reaction to obtain cefminox, adding sodium carbonate, and crystallizing to obtain cefminox sodium. According to the present invention, the steps are simple, the ladder temperature control mode is used in the reaction temperature control, the complete reaction is ensured through the material feeding time limiting while the production efficiency is improved, the quality of the prepared product is good, and the raw material utilization rate is high.