In the measurement of lightning impulse voltage,the measurement system consists of impulse divider、waveform acquirement and analysis software. Waveform acquirement and analysis soft are called second side of the impulse measurement. Usually the laboratory will periodically calibrate the lightning impulse measurement system. In the evolution of uncertainty of the total measurement system,the second side of the measurement accounted for a large proportion. The improvement of the second side accuracy is of great significance to improve the measurement performance of the overall system. The test data generator (TDG2.0.6)in IEC61083：2013 was used to test the measurement accuracy of the software in the second side of the lightning impulse measurement system. The test results show that the T1 data of the waveforms with oscillation exceeded the allowable error. To solve this problem,the interpolation and two curve fitting methods were used to ensure the accuracy of measurement software. Comparing this software with other two foreign software, the results showed that the accuracy of the three kinds of software measurement basically are at the same level.