Abstract: To separate the normal modes in shallow water under near field, a separation method based on frequencywavenumber(F-K) transform is proposed in this paper. Based on F-K transformation, the 2D receipt a-coustic signal matrix, which composed by near field horizontal multi-channel signals,is processed from time-space domain to frequency-wavenumber domain, the normal modes in signals is separated by extracting the wavenumbers at each frequency for each order in the frequeny-wavenumber domain. The reliability and validity of this method in practice are verified by numerical simulation and tank experiment, which showed that the normal modes in Pekeris waveguide under 200 Hz could be obtained reliably within 500 m through this method.