Abstract: For the acoustic radiation problems from a complex vibrating body surface, a model analysis approach is put forward. All the normal vibration velocities on a vibrating surface form the Hilbert space. And in the Hilbert space, an operator is defined, which includes the radiation property of the vibrating surface and is linear, self-adjoint and positive. Using the operator, a set of basis functions in the Hilbert space are obtained, which describe the radiation patterns and are called the radiation modes. Based on the radiation modes, a set of basis functions of the radiation field are obtained by the Helmholtz simple layer potentials, which describe the distribution patterns of the radiation field and are called the field distribution modes. The radiation behavior of the vibrating surface can be expressed by expansions of the radiation modes and the field distribution modes. The model analysis approach is introduced into the acoustic radiation problems.