Abstract: This paper studied the photosynthetic rate of Chinese fir by isotopic tracer technique. The main conclusions were as follows: 1. Various needle leaves and shoots had different abilities of 14C-as-similate. In general, the 14CO2 net photosynthesis rate of leaves in spring was larger than that of leaves in autumn in the first year. The shoots of the second year showed that maximum photosynthesis rate, the shoots of the third year were the second, the shoots of the fourth year were minimum. 2. The net photosynthetic rate of the shoots in the north was larger than that of the shoots in the south in the crown layer of Chinese fir. 3. The study of the photosynthetic characteristics of genotype of the clone system was advantageous to the early selection of Chinese fir.