The forest water balance relationships were established based on the rainfall redistribution by forests, water transpiration from vegetal strata, forest soil evaporation observed and measured in site by means of fixed standard plots method as well as ot her co ncerned f acto rs(such as runof f)deduced as balances from the simplified water balance equations. The results showed that the total evapotranspiration ranged from 476.6 to 651.3 mm for the five forest vegetation types in growth season, in which the canopy evapotranspiration was the major part, ranged 476.6～651.3 mm, accounting for 73.5%～88.6% of the total; The forest field evapotranspiration under canopy changed from 69.3 mm to 126.5 mm, making up 11.4%～26.5% of the total; The groundflow depth ranged from 69.3 mm to 126.5 mm, sharing 11.4%～26.5% of the total; Surface runoff did not easily happen in forest fields, and ground flow depth ranged 76.6～263.9 mm, accounting for 10.3%～35.5% of the rainfall amount in the same period. There was much large difference among forest types in water balance components, showing that the total evapotranspiration for conifers was apparently larger than that for hardwoods.