To study the fluctuation characteristics of the Yangtze river ro-ro freight index, the monthly data of Yangtze river ro-ro freight index, international crude oil price and sales volume of Chinese commercial vehicles are selected, and the empirical analysis is carried out by using CensusX12 seasonal adjustment method and VAR model. The results show that there is obvious seasonal fluctuation law in the ro-ro freight index of commercial vehicles. Granger causality exists between automobile sales and ro-ro freight index, and between international crude oil price and ro-ro freight index. Through impulse response function analysis, the ro-ro freight index of commercial vehicles is sensitive to the impact of itself, crude oil price and sales volume of commercial vehicles, and the ro-ro freight index of commercial vehicles responds most violently to its own fluctuation impact.