In order to improve the level of crop growth management, the characters of traditional expert system and neural network are considering, the self-learning and inference ability of neutral network and the prior knowledge of expert system were regarded as combination, then expert system of crop growth based on neural networks was constructed. The paper proposed the model of neural networks and analyzed the achievement of expert system, and carried out simulation and test on the growth management of crop. The practice has proved that this method is an effective diagnostic method, and can be applied in the growth management of crop, then improve high production and efficiency of crop.