The phasor angle difference applied in traditional Fourier frequency measurement algorithm cannot correctly reflect the real difference, resulting the principle error. Therefore, Fourier frequency measurement algorithm based on modified phasor angle difference is proposed. As phasor angle, which acts as intermediate variable, is amended by correction factor, and the theoretical error of traditional Fourier algorithm is eliminated. The algorithm is not sensitive to the noise and harmonics, which is inherited from Fourier algorithm. Besides, to overcome the paradox that traditional iterative algorithm cannot have both accuracy and speed, quadratic interpolation technology is adopted for revising the sample sequences. Simulation results show that, compared with the traditional Fourier algorithm, both computing speed and accuracy of the proposed algorithm are improved under the same hardware environment.