In order to ensure the accuracy and reliability of the measurement value of the metal oxide arrester (MOA) tester, it is necessary to calibrate it and evaluate its uncertainty regularly. The standard signal generator calibration method of MOA tester is introduced, based on the description of the characteristics of MOA and testing method. The uncertainty of calibration results of the MOA tester is analyzed and evaluated in detail. The reliability of calibration results and the rationality of uncertainty are verified by using transfer comparison method through the comparison with the calibration results provided by National High Voltage Metrological Station. This paper provides a method for the calibration and uncertainty evaluation of the MOA tester, which is helpful to improve the accuracy and consistency of the value transfer of the MOA tester.