Abstract: The Sanjiang(three rivers) Plain is situated on the northeastern part of Heilong jiang Province.The plain embraces most concentrated marsh lands and is the largest in China.The Naoli River is a typical marsh river on the Sanjiang Plain; its hydrological regime is largely a ffected by the dual factor of clmiate change and human activities.In this paper,the water balance method and empirical model are used to establish the rainfall runoffre lationship on the Naoli River.Discussions on the advan tages and disadvantages of the two approaches are given.The results show that about 40% of changes in mean annual runoffduring the period 1968 2005 are the results of climate change through the reduction in precipitation for the same period.For example,at Baoqing and Caizuizi stations,43% and 35% decreasing in mean annual runoff can be attributed to the reduction in precipitation,while the evaporation change is only responsible for 10% of such change.Our study also indicate that the water balance method may possess certain advantages over the empirical model,the latter can still be considered to be a quick and easy approach to the subject after all.