Plants have evolved some important mechanisms of adaptation to environmental stress. Plants might respond to multiple environmental factors simultaneously. The cross adaptation of plants provides mechanisms for plant survival under multiple stress conditions. Plant cross adaptation has been observed to occur under low/high temperature and drought stress as well as under saline and drought stress. Sulfur dioxide (SO₂) is a common air pollutant with harmful effects on plants. However, it is not clear how plants respond to simultaneous changes in air SO₂ concentration and availability of soil water. In this study, effects of SO₂ exposure on the adaptation of plants to drought stress were investigated using Arabidopsis. The results showed that exposure to 30mg/m³ SO₂ for 6 to 72 h significantly decreased stomatal aperture in Arabidopsis leaves. The transcriptional levels of heat shock transcription factor HsfA2 and its target genes encoding heat shock proteins Hsp17.7, Hsp17.6B and Hsp17.6C were increased after 48h and 72h of exposure to SO₂. The expression of three tested drought-responsive genes DREB2A, DREB2B and RD29A in Arabidopsis were also up-regulated in SO₂-fumigated Arabidopsis shoots after 48h and 72h of exposure. Moreover, pretreatment with SO₂ caused higher relative water content and low degrees of wilting in Arabidopsis plants under drought stress, indicating improved drought adaptation in SO₂-fumigated plants. The contents of soluble sugar and proline were increased in SO₂-fumigated Arabidopsis plants, and these increases were accompanied by increases in antioxidant enzyme activity and low malondialdehyde content. The results indicate that SO₂ exposure improves plant adaptation to drought stress through regulating stomatal closure, gene transcription and metabolic pathways. The improved antioxidant capacity and increased synthesis and accumulation of osmolytes in SO₂-fumigated Arabidopsis plants help to prevent negative effects of drought stress and to enhance plant adaptation to drought stress.