Abstract: A sidelobe suppression method using nonuniformly spaced array with aperture apodization processing was proposed for underwater acoustic imaging in near field,which was studied both in theory and experiment.The focused beamforming based on spherical wave propagation theory was used in the method.Firstl,the nonuniform array with low sidelobe was designed for suppressing the sidelobe of one-way beam pattern by spacing perturbation.Then,applying the aperture apodization technique to underwater acoustic imaging,the different size apertures for transmitting and receiving were used for further suppressing the sidelobe of two-way beam pattern.The experimental results from water tank show that the proposed method can suppress the sidelobe more effectively only with fractional mainlobe width increase.Since the method is simple-realized,the imaging system can be simplified as well as achieving improved performance.