In this paper, the regression effects, aecuracies and figures of three mathematical models for simulating light vertical distribution in rice canopy were compared. The model was the best. The quantitative relationships between a, b and LAI(z) accumulated to a height above the ground, solar altitudes were discussed. A universal available model for light distribution in crop canopy was proposed, and the error in utilizing the model was analysed. Meanwhile, daily changes in light intensity in

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... sentative layers of the canopy were described by harmonic analysis. Studying the relationship between light-distribution characteristics in crop canopy and canopy structure is of great practical significance for utilizing solar radiation energy effectively and increasing rice yields. This article alms at find a simple and useful mathematical nxxlel for light distribution within a crop canopy. 1. Materials and method of the experiment August 15,1990. It was a clear sky and the rice was in the primary stage of riming. Light intensities within different layers were measured using a GE-1 illuminometer. (made at the "Yinchuan Electrometer Factory, Ciina) within a high-yield canopy (Shennong 91-418, per unit area yield 10.35t/ha, crop height about 100cm, leaf area index LAI=6.83)and a general canopy (per unit area yield 9.21t/ha, crop height about 90cm, LAI=4.44). The experiment began at sunrise and ended at sunset. (distance between layers is 10cm) Particular time was taken around the exact hours. Meanwhile, the weight of green leaves, LAI and the specific leaf weights etc. were measured by the stratifying clip method so as to understand the vertical structure of the canopy. The vertical distributions of light and daily changes within the rice canopy are analysed using a mathematical simulation method and was verified with experimental materials.