Using this method, each canopy height of early rice is measured as a horizontal sample, and interpolation analysis is carried out on the point values of photosynthetic active radiation transmittance on each canopy height horizontal sample, so as to obtain a three-dimensional spatial distribution map of photosynthetic active radiation transmittance, which can more accurately and intuitively show the distribution characteristics of light in early rice canopy at different heights , rows and row-middle. It can be seen from the horizontal distribution maps of photosynthetic active radiation transmittance at different canopy heights that the photosynthetic active radiation intensity at the same canopy height level is not uniformly distributed. When predecessors simulated the light distribution and photosynthesis in the canopy, they usually assumed that the photosynthetic active radiation intensity at the same canopy height level was uniform, and the measured results of this method can provide data support for more accurate simulation of the three-dimensional spatial distribution of photosynthetic active radiation in crop canopy. 75- ___________ ___ 7 45. Z__ 30- _ North-south El E2 (3 E4 E5 West-east Figure North-south West-east Figure 2。