In power system，traditional method of nonsinusoidal power measurement is not feasible for containing non integer harmonics condition. A method of power measurement based on Prony algorithm is presented. At first, identify all modes of integer and non interger harmonics from voltage and current signals, using Prony method. Futher more, calculate active and reactive power in each harmonics frequency, using the modes of harmonics. Based on the defination of IEEE active power, a expression of Budeanu power is given in non integer harmonics condition. At last, active and reactive power of energy gird are calculated. The results of simulation prove that this method is feasibility. The method of power measurement based on Prony algorithm has high precision, especially for non integer harmonics condition.