OBJECTIVES: Base on 2012 AGS Beers criteria, construct a CPOE decision supporting and monitoring system to decrease potentially impropriate medication(PIM) used in hospitalized elderly patients, further enhance patient safety and reduce medical cost. METHODS: We use Hyperion search PIMs in hospitalized patients from 2010 to 2011, investigate the relationship between PIM and the physician prescriptions, patients’ characteristics, such as age, gender, diagnosis, et al. We’ll construct a CPOE decision supporting and monitoring system to help physician prescribe appropriatly, on the other hand to monitored the suitability of the medications by clinical pharmacist. We use chi-square test to examine PIM incidence before and after these two system intervention. Logisti regression to analyzed the relationship between PIM and relative risk factors. Patients’ characteristics such as gender, age, and drug category are analyzed by descriptive statistics and chi-square test.  RESULTS: After the decision supporting system implementation, Beers Criteria related improper medication prescription rate were decreased (6.42% and 5.47%). The relationship between PIMs and gender, age, prescription division, before and after decision supporting system was implemented were no significant difference. Except Hematological Oncology, PIM prescriptions rate were significantly decrease in all different department after the plan was intervention. The major PIM prescription items were Metoclopramide Inj, Lorazepam tab, Amiodarone tab., Doxazosin tab., Spironolactone tab. PIM decision supporting system initiative suggests alternative agents for PIMs in CPOE system. There were 71.4% accepted the suggestions. Otherwise, accepted pharmacists’ suggestions and adjust PIM were 92.5%. CONCLUSIONS: Drug decision-supporting system and pharmacists' interventions for reduce PIM in elderly patients is important. The decision supporting system can decrease PIM prescriptions . The efficacy of Beers criteria medication guidelines and the decision-supporting system applied to the elderly out-patient should be confirmed by further studies.