The changing color of leaves in autumn is not only necessary for the growth of foliage trees but is also important for urban landscape interests. Red color in maple leaves relates to the synthesis of anthocyanin and the degraded pigments. Ozone (O₃) is an important phytotoxic pollutant, which may affect the basic physiological functions of plants due to its highly reactive oxidative characteristics. The increased consumption of fossil fuels in China has led to increased emission of O₃ precursors and visible plant injury induced by high O₃ concentration frequently occurs around Beijing. In addition, trees are often subjected to periodic drought in North China with the frequency and the severity of drought events projected in the background of climate change. Drought in summer usually coincides with episodes of high O₃ concentrations, which, together, may affect plant growth including color expression and leaf senescence of foliage tree species in fall. Although numerous publications have reported the effects of elevated O₃ concentration or drought stress on trees, little is known about the possible interactions between anthocyanin and flavonoid in Asian maple species. To investigate the effects of chronic drought stress and elevated O₃ concentrations on leaf pigments and abscission of Shantung maple (Acer truncatum Bunge), we set up 12 open-top chambers with four treatments (AW: non-filtered ambient air and well watered; AW+60: non-filtered ambient air plus 60 nL/L O₃ and well watered; AD: non-filtered ambient air and drought; AD+60: non-filtered ambient air plus 60 nL/L O₃ and drought) in a suburb of Beijing, China. Total chlorophyll (total Chl), carotenoid (Car), anthocyanin, flavonoid, and abscisic acid (ABA) contents in early and late-flush leaves were measured in October of the first year. Leaves that unfolded from July 1 to 7 were marked as early-flush leaves and the AOT40 (The cumulative O3 exposure, which was described as the accumulated hourly mean O₃ concentrations over 40 ppb during O3 fumigation period) was 28.2 μL L^-1 h when harvested. Late-flush leaves unfolded from September 1 to 7 and the AOT40 was 14.2 μL L^-1 h when harvested. The results showed: (1) For early-flush leaves, elevated O₃ significantly decreased the total Chl and Car contents by 21% and 29.6%, respectively, increased anthocyanin and flavonoid relative contents by 34.1% and 7.3%, respectively, and increased ABA contents by 19.8%. Drought stress decreased the total Chl by 18.7%, increased the relative contents of anthocyanin and flavonoid by 37% and 7.4%, respectively, and increased ABA contents by 13%. These physiology changes would collectively lead to leaf reddening, senescence, and abscission in advance of autumn. (2) Late-flush leaves only responded to drought treatments as indicated by a significant decrease of 18.8% in total Chl and an increase of 33.4% in ABA contents. (3) Significant interactions were found in total Chl, anthocyanin, and ABA contents of early-flush leaves, as indicated by the fact that the decrease in total Chl and increase in anthocyanin were mitigated, but the increase in ABA contents was aggravated. In conclusion, early and late-flush leaves responded differently to elevated O₃ and drought stress. Early-flush leaves responded more to ozone treatment, while late-flush leaves were more sensitive to drought stress. Both treatments lead to leaf early senescence and their interactive treatments may increase the risk of early abscission. This study may provide a better understanding of autumnal leaf growth and the phenology response to elevated O₃ and drought stress in the coming future.