Objective To assess the value of serum amyloid A (SAA) in patients with acute asthma attack. Methods Sixty-four asthmatic patients in acute phase and 20 healthy individuals were included. The asthmatic patients were divided into bacterial infection-induced group and non-bacterial infection-induced group. Lung function test and chest X-rays test were conducted And inflammatory cell counts , serum SAA and CRP levels were measured. SAA were compared among subgroups of asthmatic patients and healthy controls and the diagnostic value of SAA to distinguish bacterial infection-induced asthma was estimated. Results SAA of both asthma subgroups were significantly higher when compared with the healthy individuals, and it was higher in bacterial infection-induced group than that in non-bacterial infection-induced group. In terms of ROC curve , AUC was 0.966 for SAA to distinguish merging bacterium infection, and the cut-off value was 36.67mg/L with sensitivity of 92.3% and specificity of 88.2%. Conclusions SAA increases in patients during acute asthma attack, and particularlymore obviously in bacterial infection-induced patients. It may be used as a reliable biomarker to distinguish merging bacterium infection during acute asthma attack.