A high accuracy approximation modeling approach for the acoustic-structure interaction problem with a shell structure is presented in this paper. The new approximation model aims to accurately reveal the relationship between pressure and velocity in the acoustic field. The main idea of this model is to separate the velocity terms into a combination of velocity and pressure by using a weighting parameter. The modal analysis was performed to find an appropriate weighting parameter for the new model for the spherical case. The stability range of the model is limited during this process. An approximation model was coupled with the equation of motion of a spherical shell to check the performance of the model. Responses of a spherical shell excited by a plane step wave and cosine-type incident pressure from the new model were compared to the exact solution and solutions from former approximation models such as Doubly Asymptotic Approximations (DAAs). The new proposed model can approximate high accuracy responses in both early and late time.