The key to harmonic pollution control in power grid lies is the identification of harmonic pollution responsibility. Aiming at the disadvantage that the traditional harmonic voltage responsibility index is difficult to be implemented into economic accounting, this paper puts forward a definition of the true value of the harmonic active power as a measure index of harmonic responsibility, and discusses its calculation method. In the process of discussion, the equivalent circuit principle and superposition theorem are combined, and the method of double dominant fluctuation difference quotient impedance based on relative phase angle is used to complete the definition and calculation method of harmonic active power responsibility. The calculation of practical cases show that the harmonic active power responsibility index can not only reasonably and quantitatively pay attention to the harmonic pollution responsibility of the side harmonic source, but also is simple in calculation, which is conducive to economic accounting.