In view of the practical problems existing in plant protection operations such as long premixing time, uneven premixing effect and uniformity of the premixing device of the spray, based on the existing sprayer premixing device, the basic parameters of key components such as premixing tank, premixing nozzle and feeding valve were determined by combining the pesticide formulation usage and premixing liquid delivery demand of 1000L sprayer in the field operation process. ANSYS-Fluent was used to analyze the dynamic flow field characteristics of premixing at different liquid level heights, and the dynamic distribution law of the flow field in the premixing tank was obtained. Using the quadratic regression orthogonal rotation center combination optimization test method, taking the working pressure and spatial position parameters of the premixed nozzle as the influencing factors, and the variation coefficient of the uniformity of the liquid pesticide as the evaluation index, the multi island genetic algorithm was used to optimize and obtain a better premixed parameter combination: the working pressure of the premixed nozzle is 0.3MPa, the distance from the bottom plane is 200mm, and the distance from the back vertical plane is 70mm. Field tests were conducted on powdered pesticides, and the results showed that the coefficient of variation of uniformity of the premixed solution was 32.99%. The feeding valve delivers the pesticide stably at a pressure of 0.2~0.5MPa without backflow.