Abstract: Metrological data were collected at 3 stations located in forest stands of three different tree species (Pinus koraiensis S. & Z., Larix gmelini Rupr. Abies nephrolepis Maxim.) in Heilongjiang province, Northeastern China. From these data, heat balance of these stands were calculated and compared, the results are: (1) The total, as well as the scattered solar radiation was lower than that in the open, and radiation in stands with denser closed canopy is lower than those with less dense closed canopy. Variation in radiation is greater along the horizontal direction in the stands; along the vertical direction, it was decreasing from the crown to the lower part in accordance with the law of index diminishing In the forest stand the green light is the dominant component of the radiation spectrum, because the largest portion absorbed by the tree crown occurred in the orange region of the spectrum, with red and blue regions in a lesser degree. Albedo and effective radiation in the forest stands were lower than that in the open. Balance of radiation in the forest stands was much less than that in the open, in the stands it was about 10% higher. (2) The turbulent heat exchange above the forest stands was higher than that in the open, but inside the stands, it was very weak because temperature inversion generally occurred. (3) The change of heat capacity in the forest stands was very low, generally less than 0.1 cal. 1cm²/min. (4) The total evapotranspiration in summer time was 4.8 mm per day in average, of which 4.5 mm was allocated to transpiration of the trees, and 0.3 mm to evaporation of the forest floor. (5)If the balance of radiation within stands to be taken as 100%, 55% is used for evapotraspiration, 37% for turbulent heat exchange and 8% for heat capacity chang.