This paper is based on the finite element-statistical energy analysis method(FE-SEA)establishes a prediction model for the sound insulation characteristics of carbon steel underframe floor structures in urban areas,analyzes the influence of four parameters of the floor underframe structure,rib thickness,and upper and lower plate thicknesses on the sound insulation characteristics,and selects the four structural parameters based on the lightweight principle of the Law of Mass as the judgment criterion to determine the optimal plan,and ultimately realizes lightweight acoustic optimization of carbon steel underframe floor structures.The results show that among the listed carbon steel underframe floor structural parameter optimization schemes,the carbon steel underframe floor scheme with a rib angle of 40°,a rib thickness of 0.9 mm,an upper plate thickness of 2.4 mm,and a lower plate thickness of 3.0 mm has the best lightweight acoustic optimization effect.This research can provide reference for the optimal design of lightweight vibration reduction and noise reduction of urban train body structures.