In the case of strong coupling， analyzing a complex system by finite element method costs so much due to the degrees of freedom. Although introducing modal superposition technique is able to reduce the sum of coupling system’s freedoms， it is still based on the assumption of neglecting the coupling influence between the high-order modes and low-order modes belonging to different subsystems. And it may result in non-convergence when uncoupling modes are used. Based on the undamped acoustic and vibration coupling equation， this paper presents a new coupling method called patch transfer function method （PTFM）， by which the coupling face is tackled as a series of independent patches. The patch transfer functions of each patch are calculated by the average value of the nodal value， then the coupling system PTFs can be obtained by the continuity equation. It is faster to predict the coupling system response， as the inversion of coupling equation is substituted for the transfer function from source to receiver. At last， with the model of plate and air-cavity coupling system， this paper reveals the accuracy of PTFM by comparing the result of direct coupling method （DCM）. And the theory and calculation error of the method are discussed.