The finite element method is applied to calculate the modal and vibration response of a reducer shell,and the acoustic responses of acoustic radiation power of reducer shell,air vibration velocity distribution of shell surface,sound pressure level distribution in the far field and sound pressure level in the far field point are obtained based on the modal acoustic transfer vector（ MATV） technology,the application method of MATV on the reducer shell acoustic radiation prediction are showed. Through the modal acoustic contribution analysis,the method of structure optimization to reduce noise radiation is determined. Meanwhile,the shell surface air velocity distributions provides a way of pasting damping materials in reducing the reducer shell acoustic radiation.