To make clear the influence of forests on the water quality of rainfall,the physical and chemical properties of bulk precipitation and stemflow were monitered in five different forest types,i.e.,Larix olgensis stand(Lo),Fraxinus rhynchophylla stand(Fr),mixed forest stand(Mb),Pinus koraiensis stand(Pk),and Querus mongolica stand(Mo) of secondary forest ecosystems in montane regions of eastern Liaoning Province,China.Comparing with bulk precipitation,the stemflow in five forest types was significantly acidified(P0.05),and the acidification degree was in the order of PkLoFrMoMb.The conductivity,total dissolved solids,and the concentrations of Cl-,NH+4,NO-3 and TP of the stemflow increased significantly(P0.05),while the dissolved oxygen concentration of the stemflow lowered significantly(P0.05).Among the five forest types,there were higher conductivity and concentrations of dissolved solids of stemflow in Lo and Pk,and stemflow in Lo had higher Cl-concentration.The concentrations of NO-3 and TP of stemflow in Lo and Pk were significantly lower than those in other forest types(P0.05),and the concentrations of NO-3 and TP of stemflow in Mb were significantly higher than those in other forest types(P0.05).NO-3 concentration of stemflow was significantly positively correlated with the product between diameter at breast height and tree height.These results were mainly influenced by the rainfall factors(e.g.,the length of the dry period before a rain event),stand characteristics(including leaf area index and characteristics of bark),and physical and chemical properties of substance of foliage and branch of trees etc.It can be concluded that the water quality of stemflow significantly decreased,representative of the fact that stemflow in Mb has the most effects on the chemical properties of the rainfall,and the water purity of stemflow in Pk and Lo was significantly lower than that of bulk precipitation.