Preparation method for decreasing impurities of gentamicin sulfate

The invention discloses a preparation method for decreasing impurities of gentamicin sulfate. According to the preparation method, the impurities of a gentamicin sulfate product can be obviously decreased; and the preparation can meet the requirements of China Pharmacopeia (2015) and is simple in production process and operation. The preparation method has three differences with the prior art as follows: 0.001% of triphosadenine and 0.001% of glycine are added into a spore slant culture medium; 0.001% of triphosadenine and 0.001% of glycine are added into a seed culture medium; and 0.003% of triphosadenine and 0.003% of glycine are added into a fermentation culture medium. The total impurity content of a produced gentamicin sulfate product before the improvement is more than 4%, and the sisomicin content is more than 1.5%; and the total impurity content of the gentamicin sulfate prepared by virtue of the preparation method is less than 4%, and the sisomicin content is less than 1.5%, and the micronomicin sulf