The insulation test to a combination of high-speed train flattened structure, when the swap in which two acoustic longitudinal position pad, flat top acoustic properties of composite structure changed significantly. To solve this problem, this paper based on statistical energy analysis explores the double insulation composite sheet material arranged in the order of the overall structure of sound insulation characteristics of law, analyzes the causes of the phenomenon；Subsequently, further use of statistical models to predict the impact energy method three acoustic insulation composite sheet material arranged in order of overall sound insulation properties of inquiry was extended. The results show that: for double-layer composite structure, when the two types of insulation materials is constant, the large amount of insulation material is placed near the sound source, the small amount of noise into the far end of the sound source, the lift the overall structure of the maximum amount of noise, major upgrade of the low-frequency sound insulation; For the three-layer composite structure, the situation is more complex, when the largest insulation material is placed near the sound source, the second largest amount of insulation material is placed in the far end of the sound source, the minimum amount of sound insulation material is placed in the middle, to enhance the amount of the overall structure of the maximum amount of noise, and also to enhance the low and intermediate frequency sound insulation. Contents of this paper to further improve the sound insulation properties of composite engineering has reference.