To study the operation regular pattern of road freight market and quantitatively describe the fluctuation of the road freight market, based on the statistical data of road freight industry and the dynamic operation data of freight vehicles, this paper adopts the prosperity index method, to selects indicators closely related to road freight from the dimensions of market scale, transportation efficiency, transportation price and macro environment, and to establish the road freight market prosperity index system. Meanwhile, the indicators are divided into three categories: advance, synchronization and lag by time difference correlation analysis, The monthly index of road freight market is synthesized according to the prosperity index model. Through the synthetic calculation and statistical analysis of the monthly data of road freight transportation from 2018 to 2020, combined with the actual operation of the industry, the index fluctuation threshold is studied and determined to form an early warning signal light for the road freight market to visually describe the fluctuation of the road freight market. The result shows that: road freight market has strong correlation with macroeconomic operation, showing obvious seasonal change characteristics as a whole. Meanwhile, it also shows strong elasticity and toughness. During the COVID-19, the road freight industry recovered rapidly in the shape of "V", which recovered to the normal level before the secondary and tertiary industries, fully reflecting the basic and leading role of the industry in serving economic and social development.