OBJECTIVES: To investigate antimicrobial stewardship (AMS) intervention-related effects with interrupted time series (ITS) analysis in a Chinese tertiary general hospital. METHODS: The AMS program included clinical guidelines on antibiotics, educational seminars, a multidisciplinary Antimicrobial Management Team, real-time monitoring of medical records, and controlling of the prescriptions of antibiotics against the criteria. The effect of the AMS program was analysed before (January 2011 to February 2012) and after starting the intervention (March 2012 to December 2014). Key outcomes were examined: Antibiotic use density (AUD), Antibiotic use rate and Antibiotic cost percentage in inpatient cases; Average antibiotic cost and Antibiotics cost percentage in outpatient prescriptions. ITS analysis was used to evaluate changes in level and slope for each outcome variable. RESULTS: AUD grew at 0.372 DDDs per 100 patients per month in the pre-AMS period and declined at 0.254 DDDs per 100 patients per month in the post-AMS period. Antibiotic use rate in inpatient cases decreased at 0.002 per 100 patients per month in the pre-AMS period and after the AMS go-live month, declined at 0.118 per 100 patients. Antibiotic cost percentage in inpatient cases grew at 0.002 per month in the pre-AMS period and decreased at 0.002 per month in the post-AMS period. Average antibiotic cost in outpatient prescriptions grew at 0.932 RMB per pescription per month in the pre-AMS period and decreased at 0.369 RMB per pescription per month in the post-AMS period. Antibiotics cost percentage in outpatient prescriptions grew at 0.004 per month in the pre-AMS period and decreased at 0.002 per month in the post-AMS period. CONCLUSIONS: An AMS program could be effective in Chinese hospitals and promoted rational use of antibiotics, with a significant reduction in antibiotic costs. The improvement of AMS programs are needed that could be continuously implemented to improve rational use of antibiotics long term.