In order to further improve the accuracy of the energy metering algorithms for standard electricity meters, this paper, on the basis of a more comprehensive review of the principles and performance of the quasi-synchronous sampling algorithms and fast Fourier transform (FFT) algorithms commonly used in standard electricity meters, combines the advantages of using accurate synchronous sampling algorithms for accurate estimation of the fundamental frequency and fast Fourier transform algorithms with a Flap-top window for accurate amplitude measurements, a new quasi-synchronous sampling-based fast Fourier transform algorithm with Flap-top window is constructed for energy metering. The simulation test results show that the proposed algorithm has higher accuracy and faster calculation speed than the quasi-synchronous sampling algorithm or the FFT energy metering algorithm with Flap-top window alone to measure the fundamental energy, harmonic energy and total energy under different power factors.