To provide fast and accurate measurement information， a practical method for amplitude and power measurement is proposed. By simplifying the strong nonlinear part in the DFT algorithm according to the characteristics of the real electric power network， the method takes full advantage of the DFT algorithm and uses the DFT results to compensate or modify themselves. Besides the DFT's common advantages of speediness and good performance in the presence of harmonics， the method proposed has obvious higher measurement accuracy with only an insignificant increase of the computing workload compared with the traditional DFT algorithm. The test example has validated its characteristics.