Abstract: In this paper the feature of transmission of direct light in plantation of Cunninghamia lanceolata in Huitong county was described and discussed, according to the theoretical distribution and observational data in 1982—1988. The results obtained are summarized follows:1. The direct radiant flux on the surface of canopy at southern slope is larger than that at eastern and western slope, and it is smallest at northern slope.2. The slope gradient has a great influnce on direct radiant flux on forest floor. It decreases as the slope gradient increases, except southern slope. The decrement of direct radiant flux is largest at northern slope. It shows complicated feature at southern slope. In winter half year, it increases as the slope gradient. But in summer half year, it is reversed.3. The transmissivity of direct radiant or it's flux on the forest floor decreases, under an exponential manner, as the leaf area index increases. The transmissivity of summer half year is larger than winter half year.