Abstract: 【Objective】 To reveal the effects of the growth and development of the larvae of Agrilus mali Matsumura on the main nutrients of the phloem of the infected apples. 【Methods】 In this paper, the development of larvae was investigated at fixed point for 2 years, and the content of main nutrients in different damaged parts of Agrilus mali Matsumura branches was determined. 【Results】 The results showed that the total larval mortality of phloem increased significantly, especially after mid-July, and the total mortality was much higher than that of xylem. The content of main nutrients (soluble sugar, reducing sugar, starch and soluble protein) in bast phloem was lower than that in healthy phloem. The content of persistent soluble sugar, reducing sugar, starch and soluble protein in the larval stage decreased from 38.68, 18.37, 9.47 mg/g and 19.57 mg/g in late June to 17.5, 12.15, 9.47 mg/g and 16.6 mg/g in late August, respectively. Correlation analysis showed that there was negative correlation between larva natural mortality and the content of main nutrients in phloem. The main nutrient content of affected xylem was higher than that of healthy phloem. The content of persistent soluble sugar, reducing sugar, starch and soluble protein in the larvae harm period rose from 12.13, 3.91, 3.73, 12.2 mg/g and 12.26, 14.10, 4.20 mg/g and 17.50 mg/g in late June to that in late August, respectively. Correlation analysis showed that there was a positive correlation between the larval natural mortality and the content of main nutrients in xylem(P＜0.05). 【Conclusion】 It can be seen that the decrease of soluble sugar, reducing sugar and soluble protein content in phloem of branches of Agrilus mali Matsumura was the main factor affecting the normal development of larvae, as result, it was difficult for larvae to decay into the phloem from late June to late August, resulting in a large number of deaths. This can be used as an important parameter for the population change of Agrilus mali Matsumura.