Abstract: This paper discussed the measurement of Chlorine ion content in the beer with automatic electric potential titration,the BASIC program was composed to replace he method of calculating the terminal porint potential with the seand derivative,which simplifies the complex calculation. It is shown that the Chlorine ion content in Nanchang Beer is 141.8~142.5 mg·L^-1 .The range of restoring rate is 99.7%-102.4%.The data analysis shows that this method is rather accurate with 0.29 for standard deviation and 0.2% for the variable coefficent.