Abstract: The high gap wheel sprayer has a wide range of agricultural economic market in northwest and northeast of China．In combination with working characteristics of high gap wheel sprayer and advantages of closed hydraulic system, reasonable working parameters were formulated and hydraulic system was designed to meet requirements．AMESim software model was used to build closed hydraulic transmission system, and simulation analysis was carried out according to data of hydraulic components．According to analysis results, prototype was optimized and upgraded, and verification test was carried out．Test results showed that designed closed hydraulic transmission system met actual working requirements of high gap wheel sprayer and provided a stable experimental platform for intelligent control of agricultural machinery．