Abstract: The light utilization coefficents(LUC) of poplar-crop intercropping system and pure crops(CK) were both simulated by measuring the actual parameters of crop or poplar, i.e. light intensity, maximum photosynthetic rate(PR) and quantum efficiency, leaf area index in different phenophases and light extinction coefficient of leaf curtains. The results demonstrated that, in intercropping system, the crop photosynthesis cuulating decreased with the daily light cumulating decreasing, which they were linear positive correlation. The crop PR in intercropping system was slightly higher than that in pure crop system when its relative light intensity(RLI) was more than 60%, but they were similar when RLI was less than 50%, bucause its respiration did not decrease under weak light intensity. The total LUC of three intercropping systems were higher than that of pure crop system by 27.56%～48.64%. It showed that the ratio of weighted average yield of intercropping system and pure crop system was similar to their ratio of daily photosynthesis cumulating, which prove that the simulation method is practicable.

Key words: Agroforestry, Poplar-crop intercropping system, Population photosynthetic rate, Population light utilized coefficient