The invention relates to a plant leaf area index measurement method based on the laser radar point cloud technology. Compared with the prior art, the defects that the leaf area index measurement efficiency is low, and the environment requirement is high are overcome. The method comprises the following steps of obtaining three-dimensional laser point cloud data of a plant canopy, cutting the point cloud data, conducting point cloud picture classification inside the plant edge contour, calculating the half side plant volume Vhalf of each plant, counting the number of hit points, counting the proportion of breaking points, and utilizing inversion for working out leaf area indexes. According to the plant leaf area index measurement method, by means of the three-dimensional point cloud data generated through a ground laser radar measurement system, with the combination of the computer graphics technology, the leaf area indexes are obtained from point cloud pictures for calculating needed relevant parameters and conducting multiple linear regression treatment, and therefore the leaf area indexes are calculated.