Abstract: Abstract: Variable spray technology is an effective means to improve the spray effect and save pesticide. The accurate canopy characteristic parameter detection and application rate model are the decisive stages for precise variable sprays. In order to solve the problems of low efficiency and high environmental requirements in the orchard variable spray system, in this article, LiDAR (light detection and ranging) detection technology was used to obtain the LWA (leaf wall area) which represented the characteristic parameters of tree canopy, and image processing technology was used to calculate the reference value of canopy parameters. The leaf wall area was drawn by two orthogonal images. According to the scale in the image, some coordinate points on the curve were obtained by using MATLAB, and the leaf wall area of the simulation tree was obtained by integral solution. The decision coefficient KLWA based on LWA was studied, so that the effects of foliage density and LWA on the variable spray were characterized. KLWA was determined by the weighted sums of K1 and K2, where K1 reflected the distribution density of point cloud in the tree canopy area under the average depth in the horizontal direction, K2 represented the ratio of the extreme difference in the height of the point cloud distribution to the height of the subarea within the canopy subarea. By calculating the decision coefficient KLWA in each vertical direction, and by substituting the flow function, the calculation model of pesticide dosage based on KLWA can be obtained. Using the control variable method, the multi nozzle flow model is studied. With the PID controller to rapidly stabilize the pressure and the fixed PWM frequency of solenoid valves, the multi-nozzle flow model experiment has been conducted. By calculating the duty cycle of the solenoid valve PWM and adjusting the working state of the pump and solenoid valve, so that the flow rate of the sprinkler can be adjusted dynamically to the various parts of the canopy, and variable spray based on LWA can be realized. On this foundation, A variable spray verification device was designed, which consisting of LiDAR, 10 m track, 4 nozzles, 3 artificial trees with a crown of 1.47 m, 1.70 m, 1.60 m were built outdoors and a multi-nozzle variable spray test was carried out. To explore the effect of calculation model of pesticide dosage based on LWA, 2 other conventional orchard spray methods were selected as reference sprayers for comparison in this article. The fist reference type was continuous spray, the second reference sprayer is pure quantitative spray to target. The test results showed that, the adhesion rate of the liquid spray is close 100%, indicating that the variable spray model based on LWA can achieve effective spraying. The pesticide saving rate of the variable spray application rate model based on KLWA was 68.34% compared with continuous spray. Compared with pure quantitative spray to target, the pesticide saving rate of the variable spray application rate model based on KLWA was 32.77%, and the drug saving effect was remarkable. The research method provides the basis for theoretical research and optimized design of plant protection equipment, and also references for further improving the spray effect and the pesticide utilization rate by variable spray.