Objective To observe the treatment efficacy of piperacillin/tazobactam regime for P.aeruginosa infection formulated by the method of the ratio of T above MIC (T>MIC%).Methods 59 hospitalized patients with P.aeruginosa infection were diagnosed by etiological diagnosis which was sensitive to piperacillin/tazobactam from Jan.to April.2015.Before treatment, all patients were randomly divided into the control group and the test group.Patients in the control group were treated with 4.5 g piperacillin/tazobactam once and repeated every six hours.Patients in test group were treated with 4.5 g piperacillin/tazobactam once and repeated every twelve hours.The two groups were injected by 15 mg/kg amikacin once a day based on the above program.The other treatments were kept to be same.Results Between the two groups, the clinical efficiency rate and total hospital stay were equivalent, bacterial clearance rate and incidence of adverse reactions were similar, there were no difference between CRP and APACHE Ⅱ score before and after treatment.Conclusion The regime of piperacillin/tazobactam for P.aeruginosa infection formulated by the method of the ratio of T above MIC (T>MIC%)was safe, effective and feasible.