Abstract: Intensities of photosynthesis of Chinese chestnut(Castanea mollissima Bl.)(trees and seedlings)were determined by colorimetric method under differend laboratory and field conditions,in the Shantung Pomology research institute. The treetments used were:foliar spray of essential elements to seedlings in sand culture experiments,and of some nutrient solution to mature trees;irrigation to roots or spray of water on leaves;Co₂ fertilization by increasing Co₂ concentration in the air,and application of certain growth hormones.Our results were,photosynthetic intensities of all the plants under treatments showed a higher rate than those of the controls.For example,photosynthetic rate of the seedlings in sand culture sprayed with 5% of P solution is 2.78 Co₂mg/dm²/hr.while that of the control(lack of P in sand culture)is only 2.38 Co₂mg/dm²/hr.similarly,rate of the trees under irrigation is 1.84 Co<_sub>2mg/dm₂/hr.with those of the control are 0.54 Co₂mg/dm²/hr. Among the chestnut varieties cultivated in this intitute,differences in photosynthetic intensities are also discernible.