The pesticide stress and the nutritional stress are two common adverse environmental stresses in the agricultural practice. As one kind of external stress factors, the pesticide application would affect the physiological and biochemical process of plants, such as the photosynthesis, the nutrient substance and the secondary metabolism. The nutrient substance would also affect the physiological and the biochemical processes of plants. In order to fight against the adversity, the plants would make a manifold recovery. The defense related enzymes of the plants play an important role in the fight against the adversity. The paper focuses on the effects of imidacloprid, methomyl and omethoate on the Phenylanlanine Ammonialyase(PAL) in wheat seedlings under the nutrition stress. The activities of PAL in wheat seedlings were examined after treatment by three kinds of insecticides for 5 days. It is shown that the activity of PAL in wheat seedlings cultured in the nutrient solution experiences a significant descending-raising process after being treated by 35mg/L imidacloprid. The activity of PAL in wheat seedlings cultured in water does not experience a significant raising process. The studies involving methomyl reveal similar results as with imidacloprid. After being treated by omethoate, the activities of PAL in wheat seedlings with the two treatments saw a significant difference. After being treated by omethoate for 6h, the activity of PAL in wheat seedlings cultured in nutritious substances significantly increased by 107.8%, after being treated for 24h, the activity of PAL saw a significantly decrease . Therefore, the activities of PAL in wheat seedlings might be affected by the presence of nutritious substances. The activities of PAL in wheat seedlings were influenced by the types of insecticides, as well as the concentration of insecticides and the treatment duration. Compared with wheat seedlings cultured in water, the activity of PAL of wheat seedlings cultured in a nutrient solution saw a more significant defense response.