OBJECTIVE： To investigate off-label drug use of Ambroxol hydrochloride injection， and to provide reference for further evidence-based evaluation on rationality and standardized management of off-label drug use. METHODS： All medical orders for inpatients receiving Ambroxol hydrochloride injection were selected from 10 hospitals of Guangdong province during Apr. 2014 to Mar. 2015. Situation of drug use in different categories of departments was summarized， the incidence of off-label administation route and off-label dosage were analyzed； according to drug package inserts，prescription daily dose （PDD） and drug utilization index （DUI） were calculated for each category of department， and the degree of off-label dosage was evaluated. RESULTS： A total of 761 821 person·day who used Ambroxol hydrochloride injection was included. Off-label drug use occurred in each category of departments， and the incidence of off-label drug use was 62.10％. The incidence of off-label administration route was 40.51％， mainly atomization inhalation； the incidence of it was the highest in gynecology and obstetrics department （92.70％）. The incidence of off-label dosage was 36.30％， and the incidence of it was the highest in cardiothoracic surgery department （85.36％）. Departments whose PDDs were higher than the drug package inserts were cardiothoracic surgery department， ICU， surgical department， cardiovascular medicine department， emergency department， department of internal medicine and pediatrics department. CONCLUSIONS： Off-label drug use of Ambroxol hydrochloride injection is common， and the effectiveness， safety and necessity remain controversial， which need to be proved by multi-center randomized controlled prospective trial.