Aims: This research explored the effect of exogenous abscisic acid (ABA) treatment on sugar metabolism in tomato fruits, and provided theoretical basis for the regulation of ABA on the growth and development of tomato fruits. Study Design: The whole tomato plant was treated by spraying with 50 mg·L-1 ABA. Spraying distilled water was as the control. Place and Duration of Study: College of Biological Science and Technology, between February 2019 and March 2020. Methodology: The contents of soluble sugar in tomato fruits were measured with HPLC (High performance liquid chromatography). The enzyme extraction and activities were followed the biochemical method. Results: Exogenous ABA treatment reduced the weight and transverse meridians of the fruit at the ripening stage, but increased the contents of fructose, glucose and sucrose in the fruit. At the same time, it also increased the activities of acid invertase, neutral invertase, and sucrose phosphate synthase at the ripening stage. Conclusions: Exogenous ABA treatment was beneficial to the accumulation of sugar in tomato fruit and improved tomato quality. Therefore, it could be applied to tomato production.