A method for controlling a fermentation process, the method comprising: A. collecting samples of biological cells with a flow cytometer from the fermenting tank and outputting a scatter plot comprising the current status information of the biological cells according to the biological cell samples, said status information comprising any one or any combination of cell concentration information, cell size information, cell form information, cell structure information and cell metabolism information; B. comparing said scatter plot of current status information of the biological cells with the scatter plot of the preset target status information to obtain the difference status between the current status information of the biological cells and the target status information, whereby said obtaining the difference status comprises: determining the center of gravity of the scatter plot of the current status information of the biological cells and the center of gravity of the scatter plot of said preset target status information; determining the vector characterizing said difference status, wherein the vector starts from the center of gravity of the scatter plot of the current status information of the biological cells, and points to and ends at the center of gravity of the scatter plot of said preset target status information; C. controlling the feed rate of nutrient solution flow to said fermenting tank according to said obtained difference status. A. collecting samples of biological cells with a flow cytometer from the fermenting tank and outputting a scatter plot comprising the current status information of the biological cells according to the biological cell samples, said status information comprising any one or any combination of cell concentration information, cell size information, cell form information, cell structure information and cell metabolism information; B. comparing said scatter plot of current status information of the biological cells with the scatter plot of the preset target status information to obtain the difference status between the current status information of the biological cells and the target status information, whereby said obtaining the difference status comprises: determining the center of gravity of the scatter plot of the current status information of the biological cells and the center of gravity of the scatter plot of said preset target status information; determining the vector characterizing said difference status, wherein the vector starts from the center of gravity of the scatter plot of the current status information of the biological cells, and points to and ends at the center of gravity of the scatter plot of said preset target status information; determining the center of gravity of the scatter plot of the current status information of the biological cells and the center of gravity of the scatter plot of said preset target status information; determining the vector characterizing said difference status, wherein the vector starts from the center of gravity of the scatter plot of the current status information of the biological cells, and points to and ends at the center of gravity of the scatter plot of said preset target status information; C. controlling the feed rate of nutrient solution flow to said fermenting tank according to said obtained difference status.