Abstract: Objective  To investigate the relationship between serum calcium binding protein S100A12 level and the severity of chronic obstructive pulmonary disease in acute exacerbation(AECOPD) and its diagnostic value. Methods  From November 2016 to February 2017， 40 patients with AECOPD hospitalized were enrolled and 20 healthy subjects were enrolled as controls. The hsCRP and procalcitonin (PCT) values of  AECOPD patients on the day of treatment and on the day before discharge hsCRP  were collected. The level of serum calcium binding protein S100A12 was detected by enzymelinked immunosorbent assay (ELISA). Results  Before treatment， the serum level of S100A12 in AECOPD group was significantly higher than that in healthy controls (P<0.05)， and after treatment， the serum level of S100A12 in AECOPD group was significantly lower than that in healthy controls (P<0.05) . Before treatment， the level of S100A12 in AECOPD group showed a positive correlation with hsCRP and PCT（r=0.414，P<0.01;  r=0.326，P<0.05）. There was no correlation between S100A12， hsCRP and PCT after treatment. Conclusion  The level of calcium binding protein S100A12 can be used as an indicator in AECOPD severity assessment and diagnosis.

Key words: pulmonary disease, chronic obstructive, calciumbinding proteins, Creactive protein, calcitonin