Objective To compare the clinical characteristics of chronic cough, and to establish the Modified Cough Assessment Test and the simple decision tree to improve the efficacy of etiologic diagnosis. Methods Patients with chronic cough consulted in Tongji Hospital between October 2021 and August 2023 were enrolled in our study. The patients with identified single cause were divided into 3 groups accordingly: corticosteroid-responsive cough (CRC), upper airway cough syndrome (UACS) and gastroesophageal reflux-related cough (GERC). And the characteristics of chronic cough in different causes were assessed and compared by cough questionnaires. Independent predictors of various causes were identified by multivariate logistic regression analysis and used to establish the Modified Cough Assessment Test (MCET) and to construct the simple decision tree. Results A total of 358 patients were enrolled, including 201 with CRC (56.1%), 125 with UACS (34.9%) and 32 with GERC (8.94%). "Cough with wheezing or chest tightness" (OR=3.222, 95%CI 2.144 - 4.843, P<0.001), "Cough with daytime heaviness and nighttime lightness" (OR=1.755, 95%CI 1.264 - 2.435, P<0.001), and "Cough with acid reflux, heartburn or indigestion" (OR=15.580, 95%CI 5.894 - 41.184, P<0.001) were independent factors for each group, respectively. The area under ROC curve for classification of CRC, UACS and GERC were 0.871, 0.840 and 0.988 for MCET, which were better than those of Leicester Cough Questionnaire (LCQ) (0.792, 0.766 and 0.913) and Cough Evaluation Test (CET) (0.649, 0.691 and 0.580). The accuracy of the simple decision tree for the differential diagnosis of chronic cough was 77.4%. Conclusion The simple decision tree based on the Modified Cough Evaluation Test is a simple and effective method of etiologic diagnosis of chronic cough, which can be used as a tool to improve the efficacy of clinical diagnosis in outpatient settings.