The invention relates to the field of traffic forecasting. A road traffic forecasting method comprises the steps that information collecting is carried out, namely vehicle driving related information and traffic forecasting auxiliary information are collected; driving path analyzing is carried out, so as to calculate the driving path, which takes a road as an element, of each vehicle to acquire driving path data; road traffic threshold calculation and vehicle behavior chain analysis are carried out, wherein road traffic threshold calculation is used for calculating the traffic threshold of each road in different flow states, and vehicle behavior chain analysis is used for analyzing and calculating the behavior chain of each vehicle; vehicle behavior mode analysis is carried out to analyze and calculate the travel mode of each vehicle; vehicle travel forecasting is carried out to forecast the travel purpose, the starting point, the driving path, the probability and the time of each vehicle in future; road traffic forecasting is carried out to forecast the flow, the flow patterns, the vehicle sources and the destinations of different roads at different times in future; and information releasing is carried out on a road traffic forecasting result.