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Sulfur dioxide (SO₂) is a major atmospheric pollutant and abiotic stressor. Although physiological studies on abiotic stressors have focused on fully expanded leaves, the resistance of leaf functional traits to SO₂ during individual leaf development has not been studied. Thus, this study aimed to conduct SO₂ static artificial fumigation experiments to evaluate changes in leaf functional traits and resistance to SO₂ for three common landscape tree species (<i>Syringa oblata</i> Lindl. (<i>S. oblata</i>), <i>Prunus cerasifera</i> var. atropurpurea Jack. (<i>P. cerasifera</i>), and <i>Ulmus pumila</i> ‘Jinye’ (<i>U. pumila</i>)) in Changchun City and ontogeny under SO₂ stress. Samples were collected on three days in autumn (1 September, 9 September, and 19 September 2019) for two different leaf stages (10 days and 40 days). In addition, remote sensing data were combined to explore the resistance mechanisms of broadleaf forests to different SO₂ concentration classes during different seasons on a large scale. The results showed that the chlorophyll content, leaf temperature, green-peak reflectance, and Fv/Fm (maximal photochemical efficiency) at 10 days were significantly lower than that at 40 days, regardless of sampling date or SO₂ concentration. Additionally, in general the SO₂ resistance for 10 days leaves was consistently smaller than those for 40 days leaves in 3 tree species. On 9 September, 10 days leaves of the three tree species showed different leaf resistance performances under different SO₂ concentrations in the order: <i>P. cerasifera</i> > <i>S. oblata</i> > <i>U. pumila</i>. Lastly, the extent of resistance decreased with increasing ρ(SO₂) classes in different seasons, and the SO₂ resistance was affected by season. We conclude that mature leaves are more resistant to SO₂ stress than young leaves are. These results will provide scientific guidance on artificial plant community construction and prevention of future vegetation degradation.