The phenomenon of overload operation of Expressway vehicles is particularly serious in China recently.Research on the extreme value of the vehicle load and its development trend is an urgent problem in the design of toll-by-weight mode.On the basis of statistical analysis of a highway WIM data under toll-by-weight mode in Guangdong Province,the vehicle load according to the models of the gross vehicle weight of the statistical analysis by the extreme value analysis theory to establish the pot model,gross vehicle weight distribution in the tail of the distribution function is obtained,and scientifically predict future arbitrary reproduce that may arise during the period of vehicle load value.Results show that the high speed sections of large tonnage vehicles is not accidental,in the future may also appear more large tonnage vehicle load and to pose a serious threat to the safe operation of the bridges and roads.Finally,based on the research results,the toll-by-weight standards proposed improvement suggestions and comments.It provided a useful reference for effectively control ling overloading vehicle loads.