The continuous progress of science and technology drives the development of domestic construction machinery. Now the emergence of high-power construction machinery, at the same time also brings more and more prominent noise problem, now people pay more and more attention to the noise problem of construction machinery. This paper mainly studies the sound field optimization of construction machinery cab structure based on ergonomics and mathematical modeling. In this paper, firstly, the body structure model and the cab sound chamber model are preprocessed, and the free mode and sound solid coupling mode of the locomotive body structure and cab sound chamber model are calculated and analyzed respectively. According to the analysis results of cab acoustic package, the noise contribution degree is calculated to determine the ceiling and left component with the largest contribution. The acoustic package of the rear coaming and rear coaming is optimized.