Abstract: The water use, biological characteristics, concentration of sulfur dioxide (SO₂) and meteorological data were acquired by the sap flow measurements and environmental monitoring techniques. Based on the coupling relationship between water vapor and trace gas through two-dimensional exchange of pores, the canopy stomatal conductance for SO₂ (G_SO2), canopy SO₂ uptake flux (F_SO2), and accumulated stomatal SO₂ flux (F_{SO2, st}) of four dominant tree species (Pinus manssoniana, Castanopsis chinensis, Schima superba, and Machilus chinensis) in a natural mixed conifer-broadleaf forest at Dinghushan, south China were determined. The results show that, on a daily scale, the time at which the maximum concentration of SO₂ appeared was partly overlapped the time when the maximum G_SO2 occurred, and the maximum absorption of the four dominant tree species occurred at around noon time. On a seasonal scale, the average concentration of SO₂ in the dry season (from October to March) was 10.11 nL·L^-1, which was higher than that in the wet season (from April to September), 5.41 nL·L^-1. The G_SO2 of the four species was significantly higher in the wet season than that in the dry season (P < 0.001), while the F_SO2 in the wet season was higher than that in the dry season (P < 0.001). Furthermore, the F_{SO2, st} of C. chinensis and M. chinensis were 2.16 and 2.50 mmol·m^-2, which were higher than 1.70 and of 1.91 mmol·m^-2 for P. massoniana and S. superba, respectively. The SO₂ stomatal absorption behavior of the four dominant tree species was mainly affected by factors such as vapor pressure deficit (VPD), photosynthetically active radiation (PAR) and SO₂ concentration. This research provides the basic data for the reasonable evaluation of SO₂ absorption flux in mixed coniferous-broadleaf forests in the Pearl River Delta region, and provides a basis for risk prevention for environmental assessment.