Abstract: Objective To examine antimicrobial usage among inpatients in tertiary first-class hospitals in China and to evaluate intervention effects of management policy for providing references to future policy intervention.Methods Data on antimicrobial usage among inpatients in 183 tertiary first-class hospitals across China during the period from 2011 to third quarter of 2015 were collected from National Center for Antibacterial Surveillance (CAS).The quantity and the number of types of antibacterial used,costs,defined daily doses (DDDs),and the ratio between rank order number of cost and rank order number of DDDs for an antibacterial were analyzed comprehensively.Results The number of various types of antimicrobial used was reduced by 129 from 2011 to third quarter of 2015,with the greatest reduction in the usage of fluoroquinolones.The greatest reduction in antimicrobial usage costs (24.98%) and DDDs (15.92%) occurred between 2011 and 2012,but then both the costs and DDDs increased and the costs increased rapidly.Among all antimicrobials used during the period,the average proportion of cephalosporins was the highest for the number of types (25.85%),costs (38.80%),and DDDs (46.35%).The costs for carbopentem and other β-lactam antimicrobials (aztreonam) increased yearly,with the growth rates from 12.20% to 22.53% in the study period.For all the antimicrobial usages,the costs of meropenem was the highest,accounting for 8.23% of the total cost during the first three quarters of 2015;the costs of imipenem/cilastain sodium usage was the second highest from 2013,accounting for 4.93% of the total cost of during the first three quarters of 2015.The two highest DDDs values were for levofloxacin and cefuroxime usage and showed a continuous increasing trend during the period,accounting for 9.04% and 5.91% of the total DDDs for the first three quarters of 2015.The antimicrobial usage with the maximum ratio (2.40) between rank order number of cost and rank order number of DDDs is fluoroquinolones and that with the minimum (0.39)is carbopentem and other other β-lactam antimicrobials (aztreonam).Conclusion After the implementation of a series of antimicrobial management policies,the number of types and DDDs of antimicrobial used were controlled effectively but the cost of antimicrobial usage was not under strong control among inpatients in tertiary first-class hospitals.Cephalosporins are most frequently used in the hospitals;the increased usage of antimicrobials categorized as limited and specific medicine aggravates economic burden of patients.