Abstract: In this investigation we have determined that the standing crop of a Chamaecyparis obtusa plantation of 21 years was 160 t/ha, the increment, 16.5t/ha·a； and the net solar energy utilization ratio 0.64% by combining the correlative growth method with the stratified crop method. This ratio was not high in the Fu Ku Ka district, Japan. From the relationship between the weight of dry matter and D2·H correlative growth, the vertical distributions of dry matter in different storeys were calculated. The seasonal changes of solar radiation energy in the top canopy and the different storeys inside were investigated with a sun-station system reader model 700, which also gives the graph of the productive structure. From our results of investigation on the locations of the leaves in different parts in canopy, we suggested that the crowns with full closed canopy in a Chamaecyparis obtusa plantation can be divided into cone and cylinder crowns as the crowns in a Cryptomeria japonica plantation. Their leaf area indices and leaf densities were 35±5cm2/g, 495g·/m3； 45±5cm2/g· and 222g/m3 respectively. The effects of the productive structure in a stand on solar energy utilization were also discussed, according to volume analysis, community productive structure as well as the distribution of solar energy.