Measuring the growth curve is mainly to measure the concentration of bacterial liquid at different time points, which can be accomplished by cell counting, making spore suspension, adding equal volume suspension to the culture medium, filtering at different time points, gravimetric measurement and other methods. A certain amount of bacteria are transferred to fresh liquid culture medium, and cultured cells will go through four stages under suitable conditions: delay period, logarithmic period, stable period and decline period. The growth curve of bacteria is drawn with culture time as abscissa and logarithm of bacterial number or growth rate as ordinate. Different bacteria have different growth curves under the same culture conditions, and the growth curves drawn by the same bacteria under different culture conditions are also different.