Abstract: When fast Fourier transform（FFT） is used to analyze the electromagnetic interference（EMI） spectrum,the measurement bandwidth effect must be taken into consideration to obtain results that are consistent with the measurement of the EMI receiver,and thus the frequency components within the EMI receiver measurement bandwidth should be superimposed at the center frequency.A spectrum analysis method based on FFT and considering the measurement bandwidth effect was proposed in this paper.Firstly,the time domain signal with traditional FFT was analyzed.Then,the results were analyzed based on windowed filtering and inverse fast Fourier transform（IFFT）.In order to save the calculation time,an improved IFFT method was introduced.The experimental results indicate that the proposed spectrum analysis method is accurate and fast.