Abstract: In order to know the influence of Larix gmelinii Plantations at eastern mountainous region in Heilongjiang province on the water quality,the water quality indexes in precipitation,throughfall,stemflow and runoff has been studied through the apparatus of water quality monitor and the method of atom absorb.Which include pH,DO,TURB,COND,ORP,K,Na,Ca,Mg,Cu,Zn,Mn and Fe etc..The results show that the value of pH varies unconspicuously in the precipitation, throughfall,stemflow and runoff,and the variance coefficient is lower.After precipitation passing through Larix gmelinii Plantations,the DO reduce gradually,the TURB and COND increase obviously.The ORP reduce gradually.The total average concentration of Na,Ca and Mg increase gradually.The net eluviation amount of K and Ca is higher than other elements of throughfall and stemflow.The net eluviation amount and eluviation coefficient of every element in stemflow is higher than that of throughfall.The runoff has the catabatic effect to acidification of water quality.