Abstract: Abstract Objective：To investigate the change and significance of stem cell factor(SCF)level in serum of patients with acute exacerbation of bronchial asthma，To explore the relationship of asthmatic patients with acute exacerbation SCF、T-IgE、FEV1 and FeNO. Methods：65 patients with acute exacerbation of bronchial asthma were divided into 3 groups with severity，37 normal subjects as control.The level of serum SCF 、EOS of 65 patients in each group were measured.The level of serum T-IgE, FEV1%and FeNO were tested quantitively.Results：Serum SCF levels in moderate and severe group were higher than that in control group and slight groups.(P<0.05). Serum SCF levels in asthmatic was higher than that in control group before treatment.(P<0.05). In asthmatic patients the level of SCF level did not correlate with EOS、T-IgE and FEV1% of predicted value,but it corrlated positively with FeNO（r=0.447，P=0.004）. Conclusion：The level of serum SCF maybe estimate accurately response airway inflammation changes,it maybe related to the severity of asthma attack.

Key words: asthma, stem cell fator, feno, acute exacerbation, forced expiratory volum at the first second