The freight traffic volume is a main reference for the planning of waterway grade and construction criteria. According to the characteristics of waterway network region and referencing the four-step estimating method on the road traffic, this paper presents a freight traffic volume estimating method in the waterway network region, with a stress laid on the waterway OD investigation, water freight traffic volume estimating model.It also researches the normal, increasing and transferring freight traffic volume estimating models. Furthermore, the freight traffic volume estimating method in the waterway network region is expounded based on the practice in the inland waterway network of Jiangsu province.