The core model of LAHARZ is a semi-empirical numerical model based on the  hydrodynamics model and combination with the analysis on the lahars of nine volcanoes. The lahars in four high easy-happening rivers, Erdaobai River, Songhua River, Yalu River and Tumen River, are simulated by the LAHARZ based on the 1∶250 000 digital elevation model. The results show that the flow distance and the damage scale were influenced by the different thresholds, which is similar with the historical lahars’ extent. The damage grades are divided into four levels as 40 km, 70 km, 80 km and 100 km. It is important for the planning and construction in the Changbai Mountain area.