[Objective] In order to improve the accuracy and reliability of the results of the determination of fat content in milk by Gerber method. [Method] This paper studied the fourth method of GB 5009.6—2016 Gerber method,analyzed the problems encountered in the operation process. [Result] The key nodes such as the total volume of the solution and the control of the adjustment time are optimized to clarify the parameters such as sulfuric acid concentration and standing time. [Conclusion] The test results are stable and accurate,and meet the daily testing of the laboratory,which is especially suitable for production enterprises and grassroots testing institutions.