OBJECTIVE:To discuss the application of Prescription Automatic Screening System (PASS) in the examination of clinical medical orders. METHODS: The level and type of caution and the modification rate of medical orders in our hospital between April 2005 and April 2006 were analysed statistically, and the conformity between PASS cautions of medical orders and clinical medications was evaluated. RESULTS: A total of 10 982 160 medical orders were monitored by PASS, of which, 11 146 were with black cautions and in which 2 861(25.67%) were modified, 51 504 were with red cautions and in which 10 357 (20.0%) were modified, 339 449 were with yellow ones and in which 66 022 (19.45%) were modified. In PASS monitor process, inconformity between feasible clinical medical orders and cautions of PASS was noted in a few cases. CONCLUSION: The examination of medical orders using PASS is convenient and rapid and the PASS can help improve clinical rational drug use level, however, its function of remains to be updated and optimized.