In this paper, the virtual instrument technology LabVIEW as a software platform, combined with NI-USB6009 data acquisition card is used to measure DC voltage and both the amplitude and the frequency of sine wave of the signal generator. The statistical result of the measurement shows the normal distribution. For the periodic signal, increasing of sampling quantity per period can reduce the standard deviation of the frequency, and can cause improving the accuracy of frequency measurement. This experiment can be designed for students to study the normal distribution law of random error through practical measurement.