Abstract: The aluminum-steel structure is often applied to high speed vessels for the purpose of weight reduction, declining center of gravity, and high speed. The transition joint between the steel-made main hull and aluminum alloy superstructure could affect the propagation of structure acoustic waves, thus affecting the Coupling Loss Factor (CLF) between these structures, a key parameter of Statistical Energy Analysis (SEA) and significantly impacts the prediction of noise. Based on the finite element energy flow method, a numerical computation model and corresponding calculation program in Matlab are developed, which are then verified with experiment and L model's wave approach results. The influence of calculation parameters on accuracy is studied and relevant suggestions are given. Particularly, the effect of joint parameters on CLF is studied, suggesting that the thickness ratio of plate and joint has a large impact?to the CLF; the energy flow features of the stiffened plate model is studied, indicating that compared with the flat model, the CLF curve of the stiffened plate model is more mild. Overall, the proposed program and the findings in this paper provide guidance for noise prediction and reduction in marine engineering.