[Objectives] To determine the aerobic plate count (APC) in the milk samples, evaluate the uncertainty of the test results, and to provide a scientific basis for the quality control of the testing process. [Methods] In compliance with the national food safety standard Food Microbiological Examination: Aerobic Plate Count (GB 4789.2-2016), the aerobic plate count in the milk samples was detected. The source of the uncertainty of the test result was analyzed and a mathematical model was established in accordance with Evaluation and Expression of Uncertainty in Measurement (JJF 1059.1-2012). Then, the introduced uncertainty components were evaluated to determine the uncertainty of the final combined aerobic plate count. [Results] The expanded uncertainty of the test result of the aerobic plate count in the milk samples was 0.043 4, and the logarithmic value interval of the results was (3.924, 4.010), and the antilogarithm was taken to get the aerobic plate count in the sample to be 8 395-10 233 CFU/mL. This method can effectively evaluate the uncertainty of the aerobic plate count, and ensure the accurate and scientific laboratory test data.