Abstract： Background The performance of asthma control test (ACT) at baseline for predicting future risk of asthma exacerbation has not been previously demonstrated.This study was designed to explore the ability of the baseline ACT score to predict future risk of asthma exacerbation during a 12-month follow-up.Methods This post hoc analysis included data from a 12-month prospective cohort study in patients with asthma (n=290).The time to the first asthma exacerbation was analyzed and the association between baseline ACT scores and future risk of asthma exacerbation was calculated as adjusted odds ratio (OR) using Logistic regression models.Further,sensitivity and specificity were estimated at each cut-point of ACT scores for predicting asthma exacerbations.Results The subjects were divided into three groups,which were uncontrolled (U,n=128),partly-controlled (PC,n=111),and well controlled (C,n=51) asthma.After adjustment,the decreased ACT scores at baseline in the U and PC groups were associated with an increased probability of asthma exacerbations (OR 3.65 and OR 5.75,respectively),unplanned visits (OR 8.03 and OR 8.21,respectively) and emergency visits (OR 20.00 and OR 22.60,respectively) over a 12-month follow-up period.The time to the first asthma exacerbation was shorter in the groups with U and PC asthma (all P＜0.05).The baseline ACT of 20 identified as the cut-point for screening the patients at high risk of asthma exacerbations had an increased sensitivity of over 90.0％ but a lower specificity of about 30.0％.Conclusion Our findings indicate that the baseline ACT score with a high sensitivity could rule out patients at low risk of asthma exacerbations and oredict future risk of asthma exacerbations in clinical practice.