OBJECTIVE: To analyze and evaluate the effectiveness through the pre-review mode for medical orders with the clinical drug use decision support system

so as to provide empirical reference for the review of medical orders.METHODS: By using the clinical drug use decision support system and combining with the manual review of clinical pharmacists

the pre-review mode for medical orders was established.Review rate of medical orders for inpatient medical orders in Chui Yang Liu Hospital Affiliated to Tsinghua University were compared before implementation of pre-review mode（ from Jan.to Aug.2018） and after implementation of pre-review mode（ from Jan.to Aug.2019）.Meanwhile

400 inpatient medical orders were collected retrospectively before and after the implementation of prereview mode

and the rationality of medical orders was evaluated to compare and analyze the changes of irrational drug use.RESULTS: Compared with before implementation of pre-review mode

after implementation of pre-review mode

the review rate of medical orders increased from 45.09%（ 204 500/453 500） to 100%（ 511 400/511 400）

with statistically significant difference（ P < 0.05）.The number of medical orders in the inpatient medical orders drawn before and after the implementation of pre-review mode was 12 759 and 13 343

respectively.The rate of irrational drug use in the inpatient medical orders decreased from 4.13%（ 527 items） before the implementation to 1.42%（ 189 items） after the implementation

with statistically significant difference（ P<0.05）.CONCLUSIONS: The pre-review mode for medical orders with the clinical drug use decision support system can effectively promote clinical rational drug use in the hospital.