Objectives. To observe changes in blood glycemic variations and oxidative stress level before and after dapagliflozin treatment in patients with newly diagnosed T2DM. Methods. This was a randomized, double-blind, placebo-controlled, phase 3 trial. A total of 28 patients with newly diagnosed T2DM with HbA1c levels of 7.5-10.5% were randomly selected to receive dapagliflozin or placebo treatment for 24 weeks. After baseline data were collected, we analyzed glycemic variations and plasma 8-iso PGF2α level at baseline and at the endpoint. Primary outcome was the changes of mean amplitude glycemic excursion (MAGE) within groups. Results. After 24-week dapagliflozin therapy, our data showed the significant improvement of MAGE with dapagliflozin therapy (P = 0.010). Compared with control group, patients in dapagliflozin group exhibited reduction in 24-hour MBG (P = 0.026) and lower mean plasma glucose concentrations, especially during periods from 2400 to 0200 and 1300 to 1800 (P < 0.05, resp.). In addition, plasma 8-iso PGF2α level was notably decreased in the treatment group compared to the control group (P = 0.034). Conclusions. In conclusion, this study shows the ability of dapagliflozin to improve glycemic variations and associate with reduction of oxidative stress in patients with T2DM, which may benefit the cardiovascular system.