The mixed artificial Pinus tabulaeformis and Pinus armandi forests are the main community type in the upper reaches of Minjiang river. By using the method of water balance, the contents of crown-interception, throughfall,stemflow are studied. Through 24 precipitation located observation in the forests distribution,the results shows that the canopy interception,throughfall and stemflow of the mixed forest are 83.47 mm, 81.43mm and 2.00 mm,respectively. Which accounts for 11.4% ,69.0% ,19.6% of rainfall in the same time. The relationships between canopy interception and rainfall could be described significantly by a power function,while the relationship between tbroughfall,stemfall and rainfall is linear. The results indicate the effects of the mixed forest ecosystem on water preserving capability and soil and water conservation is significant.