Abstract: For active power of AC power, parameterized-definition test method is discussed.The approach for testing the active power according to power definition in engineering application is researched based on correlation analysis theory in detail and its inherent antinoise characteristic is proposed.Test performances of the two approaches are analyzed and compared.Experiment results show that compared with the parameterized test method, the approach based on the definition of active power can reduce number of the sample data for the analysis by about two times and the noise amplitude can be permitted from less 3% to 12% of signal amplitude.