Acoustic emission technology of crop disease stress will be the important tendency of pesticide application information in the future. With analyzing relationships among crop disease stress degree, acoustic emission and environmental factors, precision spraying system based on acoustic emission for crop disease stress was designed in the paper. Self-learning fuzzy arithmetic for precision spraying to field was put forward. The model was simulated successfully with the Matlab platform. The result showed an expected effect for the spray rate control system. The study provided a new control strategy and method to realize intelligent control of precision spraying for crop.