It is much valuable to find a method for predicting the middle and high acoustic characteristics of big and complex structures such as ships and airplanes. Impact of the ring frequency and the damping on the vibration transmission is discussed firstly. Then the feasibility of the model simplification method for big and complex structures whose acoustic characteristics will be predicted is analyzed. At last, the simplification method was applied to predict the middle and high frequency sound radiation of the double complex cylindrical structures. Numerical results showed that the proposed method has the same accuracy as the conventional finite element method and boundary element method, and can be applied to deal with engineering problems.