【Objective】Dynamic variation of protein and mechanism of nitrogen accumulation and degradation in southern fruit tress were studied in the experiment，and correlation analysis was conducted between nitrate nitrogen and protein metabolism to provide references for rational fertilization and scientific management of fruit trees. 【Method】Using the leaves of autumn shoots from three evergreen fruit trees: mango， longan and litchi as test material， total protein content and nitrate-N content in leaves during spring and summer were determined by Commassie Brilliant Blue Staining and Salicylic Acid methods， resepctively. 【Result】The results showed that the total protein content in the leaves of mango， longan and litchi all decreased firstly and increased afterwards with“V”type variation， the average protein content in leaves of three fruit trees followed the trend: longan （18.03 mg/g）＞mango（11.57 mg/g）＞litchi （2.53 mg/g）. The nitrate nitrogen content in leaves of litchi and mango showed stable increasing trend， while that of mango decreased firstly and increased afterwards. 【Conclusion】There was no significant correlation between nitrate nitrogen and protein metabolism in leaves of southern fruit trees. The storage protein in leaves may be a key nitrogen source for fruit tree growth in early spring， its content variation could be reckoned as an importatn indicator for reasonable fertilization.