The wide use of non-linear loads causes significant harmonics pollution to the electrical network.How to measure electric power accurately and electric energy reasonably in the presence of harmonics has become an urgent problem in the research field of electrical measurement technologies and instruments.The key to the electric energy measurement is accurately measuring the active power.In this paper，an adaptive notch filter（ANF）-based fundamental-frequency and harmonic active power respective measurement method is proposed on the basis of the single-phase instantaneous power theory.The fundamental-frequency，each order harmonic and their orthogonal components of the single-phase voltage and current are separately extracted by ANF，and then fundamental-frequency and each order harmonic active power are calculated respectively according to the single-phase instantaneous power theory.Simulation and experiment results indicate that the new active power measurement method proposed in this paper has high level metering accuracy.Particularly when the power frequency varies，this method is still able to measure the fundamental-frequency and each order harmonic active power correctly and fast without additional frequency measurement and synchronous sampling.