Abstract: Because of the strong reverberation in shallow water waveguide,the localization performance of small targets degrades when using the monostatic sonar.To solve the above problem,an acoustic barrier experiment using forward scattering has been made on the lake.This work localizes small targets under non-isovelocity condition in natural environment,by utilizing the location information contained in the sensitivity kernel for the perturbed eigenrays in two steps,choosing effective perturbed eigenrays from numerous candidates and then localizing the targets according to the spatial distribution of sensitivity kernels.The results suggest that this method is able to locate a 0.4-m-diameter sphere by using the LFM signal in the 20-28 kHz frequency band.Moreover,this method demonstrates good robustness to target material and size mismatch.