Abstract: The water quality of rainfall,through-fall,stem-flow,litter-through and runoff in Pinus koraiensis plantations of the eastern mountainous regions of Heilongjiang Province were studied.Water quality indexes,pH，DO(Dissolved oxygen),TURB(Turbidity),TDS(Total dissolved substances),K,Na,Ca,Mg,Cu,Zn,Mn and Fe were also analyzed.The results show a remarkable change in the chemical properties of rainfall after passing through the forest canopies.There is an observed decrease in pH and DO,obvious increase in TURB and TDS,and different degrees of increase in other chemical elements.With the exception of Cu,higher element contents are found in stem-flow than in rainfall and through-fall.The variance coefficients of all elements show remarkable increase in through-fall and stem-flow.With the exception of Mn,the variance coefficients of the elements in litter-through are lower than those in the other water media.The amount of chemical leaching of K and Ca is higher and that of Cu and Zn lower in through-fall,stem-flow and litter-through.The leaching coefficients of the elements in through-fall are observed to be in the following order:Mn＞K＞Mg＞Cu＞Fe＞Ca＞Na＞Zn.The order for stem-flow is:Mn＞Mg＞K＞Fe＞Ca＞Cu＞Na＞Zn,and that for litter-through is:Mg＞Mn＞K＞Fe＞Ca＞Cu＞Na＞Zn.