According to the phase error mechanism on the asynchronous sampling condition of discrete Fourier transform（DFT）， a virtualαβ stationary coordinate contained two reversed-phaseβ axis is constructed by utilizing two forms of positive sequence component expression underαβ stationary coordinate. A new phase measurement algorithm synthesized with different proportion of three data window DFT results multiplied by different coefficients is proposed， which could greatly eliminate the dynamic part of phase measurement error of traditional DFT. After compensating the fixed offset， we can get the precise phase angle measurement results. The simulation results show that the proposed algorithm has high accuracy， small computation and real-time performance.