Abstract: In order to improve the level of mechanized pest control and pesticide application technology of crops with high stalk such as sugarcane, and solve the problems existed at present including field entry difficult, pesticides dosage large and utilization rate low for common sprayers, a variable-rate spraying system for the high clearance wide boom sprayer based on 3D LiDAR real-time scanning was developed. The sprayer used for the system had a width of 24 m, a ground clearance of 1.35 m and an adjustable boom height from 0.5 to 2.5 m. 16-line 3D LiDAR sensor was adopted to detect the three-dimensional information of crops in real time. The PWM（Pulse-Width Modulation）controller installed on the rear of the machine obtained the speed information of the sprayer from the CAN bus and transferred it to the computer in the sprayer cab. The control program was set up by Python software, and the relevant spray quantity prescription map was drawn by integrating the scanning data of LiDAR and real-time speed information, then the information obtained was sent out to PWM controller, each of which controlled one stage boom. A mathematical model between the crop canopy height and duty cycle of the solenoid valves was established to obtain the needed spraying volume by controlling the opening and closing of the solenoid valves by the controller. In order to verify the accuracy of the variable-rate spraying system, after the system was assembled, field tests were carried out in sugarcane fields in Guangxi province. The results showed that with the change of sugarcanes plant height, the maximum error between the height of sugarcanes scanned by LiDAR and measured was 8.42%, the minimum error was 0.17%, and the average error was 4.59%, the LiDAR had a good accuracy in scanning and identifying sugarcane height. The recognized information could be accurately transmitted to the variable-rate spraying system. When the variable-rate spraying system opened, the droplet density changed with the plant height，the higher the plant height, the greater the spray volume, and the higher the droplet deposition density. When the average plant height changed from 1.50 to 1.76 m, the droplet deposition density increased by 73.37 drops/cm2, and the minimum droplet deposition density was 34.2 drops/cm2, which was higher than the requirements of GB/T 17997-2008 not less than 30 drops/cm2, the maximum coefficient of variation of droplet deposition density in upper, middle and lower layers of the plants was 13.19%, which met the requirements of NY/T 650-2013, the variable-rate spraying system could meet the requirements of pest control and could achieve pesticide application on demand. The total amount of pesticide application was 56.43 L for variable-rate spraying, which was 22.53 L and 28.5% lower than 78.96 L of constant-rate spraying. This study provides a new idea and method for the high-efficient and precise control of plant diseases and insect pests, and provide a reference for the structural design of new precision variable-rate spraying machines.