This paper employs advanced optimal techniques to design an acoustic lens composed of an anisotropic metamaterial. The structure of the optimized lens consists of random rigid scatters embedded in a matrix, in which the sizes of the scatters are treated as design variables of the optimization problem. The numerical examples demonstrate that the optimized lens can focus plane waves onto a focal region of subwavelength scale. At the focal distance of , the optimized design achieves subwavelength focusing, characterized by a full width at half maximum (FWHM) of, along with a high sound pressure level (SPL) of 14.7 dB at the focal point. This performance surpasses the diffraction limit, owing to the enhancement of evanescent waves through multiple scattering. Moreover, the optimized lens can offer a potential for a wide operating frequency range.