The invention relates to a semi-continuous gentamicin Cla production method based on control of a specific growth rate. The method comprises the steps of primary seed culture, secondary seed culture and fermentation production. In the fermentation production process, by supplementing a fermentation broth with materials and water and controlling discharge of the fermentation broth, the culture volume of the fermentation broth is kept constant, and the specific rate is kept in a range of 0.015-0.025 h<-1> in the fermentation process. Compared with the prior art, the process method effectively keeps metabolic activity of gentamicin Cla continuously at a product synthesis stage, prolongs the culture cycle to 300 h and greatly improves the production efficiency. The process method determines that in the actual semi-continuous fermentation production process, keeping of the specific rate in the range of 0.015-0.025 h<-1> in the fermentation process is most beneficial to product synthesis.