Recent studies have shown that B7-H3, a recently identified B7 family member, plays a critical role in the development of asthma.This study is to explore the expression of B7-H3 in children with asthma exacerbation.Twenty-one Chinese children with asthma exacerbation as well as 18 nonasthmatic control Chinese children were enrolled. B7-H3 level and cytokines (interferon [IFN]-γ, interleukin [IL]-4, and IL-10) determination were performed by enzyme-linked immunosorbent assay (ELISA) technique. Meanwhile, clinical parameters including laboratory findings, forced expiratory volume in one second (FEV(1)) and fractional exhaled nitric oxide were obtained.Children with asthma exacerbation had significantly higher levels of B7-H3 than controls (4.46 ± 1.33 versus 3.42 ± 1.48 ng/mL; p = 0.027). Plasma IL-4 level was significantly higher in asthma exacerbation subjects than controls (157.98 ± 21.57 versus 121.92 ± 24.37 pg/mL; p < 0.0001), and IFN-γ level was significantly lower in asthma exacerbation subjects (292.73 ± 152.47 versus 421.78 ± 145.84 pg/mL; p = 0.0107). Level of B7-H3 in asthma exacerbation subjects with inhaled corticosteroid (ICS) treatment recently was significantly lower than subjects without ICS treatment (t = 2.706; p = 0.0136). Additionally, levels of B7-H3 decreased remarkably after prednisone treatment. Level of sB7-H3 in asthma exacerbation subjects was inversely correlated with level of IFN-γ (r(p) = -0.605; p = 0.005) after adjustment.B7-H3 may play an important role in asthma exacerbation and was a useful clinical biomarker to evaluate asthma exacerbation.