Abstract：As the short travel time of ringing and reverberation in water body of extra-shallow sea,it results in mix with primary reflection easily and makes such processing measures as predictive de-convolution difficult to be effectively used. For that reason, according to the kinds of multiples in water body, the paper deduced theoretically the e-quations of response in both time domain and frequency domain respectively and conducted forward modeling for a four-layers' medium model on that basis, among which the first layer is sea water, the depth of which changes from 6m to 50m. The modeled results showed the differences in polarity and strength exist among the different kinds of multiples in water body; multiples of water body mixes with primary reflections, and difficult to be separated in shallower depth of sea water; along with increasing the depth of sea water, the multiples of water body and primary reflections are gradually separable, and the moveout between them increases,and energy of multiples is gradually attenuated as well, which makes them to be identified easily.
