Abstract: An improvement of frequency domain notch filtering is given,based on the analysis of frequency domain algorithms by introducing coefficient of variation(CV) as a selecting metric.The CV metric switches fast Fourier transform(FFT) notch filter off and turns to matched filter(MF) when jammer-to-signal ratio(JSR) is low,and vice versa.Both analysis and simulation showed that the algorithm has better adaptive capability in suppressing narrowband interference(NBI) and that the CV is effective as a switching metric.