Abstract: In order to select the best conditions of deficit irrigation, the three irrigation levels: the mild, moderate and severe irrigation levels were designed to study on the influences of regulated deficit irrigation on the nutrition quality and flavour components of tomato fruits. The results show that the water content of the fruits is decreased, while the contents of vitamin C, soluble solids and the sugar to acid ratio are increased significantly in severe deficit irrigation condition, and meanwhile, the titratable acid content is the highest in the moderate irrigation condition. 113 kinds of flavor components are identified in four water levels including the control, among these components 11 kinds of tomato character impact compounds such as 1-Pentanol, 2-Isobutylthiazole, Hexanal, 2-Hexenal, beta-Citral,(E)-2-Heptenal, Methyl Salicylate, 6,10-dimethyl-5,9-Undecadien-2-one, 6-methyl-5-Hepten-2-one, 1-Penten-3-one and beta-Ionone. The amounts of character impact compounds are the highest in the moderate water level, while the least in the control level. The amount of aroma component in the severe level is more than those of other treatments.