Objective To investigate the changes of stem cell factor（SCF） level in serum of asthma patients before and after acute exacerbation.Methods The serum SCF was detected in 30 asthma patients respectively in the onset period and catabasis by ELISA.The SCF levels were also determined in 20 normal subjects as control.Results the content of serum SCF of the asthma patients during the acute attack was increased significantly than normal subjects [（156.8±82.6）pmol/L vs （61.5±15.4）pmol/L，Plt;0.001]，and decreased significantly in remission [（66.2±15.8）pmol/L，Plt;0.001].Conclusions SCF may participate in the pathogenesis of asthma.