The problem of excessive noise in the cabin of the fully built ship can be effectively avoided by using a fast and effective method to control the cabin noise at the design stage. A three-layer acoustic insulation model of a 50mm marine composite rock wool board is built and its sound insulation is numerically calculated based on the wave analysis method. It is found that the sound insulation calculated by the wave analysis method is much larger than that measured in the lab. It therefore considers the influence of the sound bridge between the two composite rock wool boards on the overall sound insulation. The numerical results then agree well with the experimental results from 100 Hz to 1 600 Hz. This method can quickly calculate the sound insulation of the composite rock wool board. It is helpful for the designer to control the cabin noise at the design stage.