With the increasingly stringent requirement of wide area measurement system for the dynamic performance of synchronous phasor measuring unit

the application of digital filter in the device tends to become complicated. In order to improve the accuracy

multiple filters often have to cooperate with each other to complete the calculation. This paper gives a detailed filter design of synchronous phasor measuring unit for intelligent substation. Finite impulse response(FIR)filter cascade discrete Fourier transform(DFT)will bring about a very large amount of computation pressure on the embedded device. This paper deduces the formula of filter coefficients after FIR cascade DFT. These coefficients calculated by offline formula can significantly reduce the calculation workload and solve the computation problem caused by the filter cascade. Theoretical analysis and practical test show that measuring accuracy is up to requirement of the relevant standards after adopting the above scheme.