Background : The necessity of unify and standardize codes used at hospital has been emphasized since OCS (Order Communicating System) was adopted. Therefore, the purpose of this study were to standardize operation code by continuous training of the ICD-9-CM code that is used as standard code in OCS program at operating room. Method : In 400 operation data, operation code entered in OCS program at operating room was compared to operation name recorded in medical record. In addition, a matching rate between input data of operation code by medical record department and computing input data of operation code in 3,710 cases was compared for each department. User operation name and operation code were matched and major diagnosis by operation department and operation name were also matched. Results : User operation name was reflected in operation classification code in detail, and operation code entered on user was registered. Input rate and matching rate of operation code were gradually improved after improvement activity. In particular, a matching rate was high at ophthalmology where operation name is segmented. Plastic surgery and orthopedics with a lot of emergency operation and comprehensive operation name show low input rates. Conclusions : As the medical field makes progress in computerlization, awareness of information exchange and sharing becomes higher. Among codes to classified medical institution, codes related to surgical operation are all different by user of hospital and department. Computerlization and standardization is essential. And when efforts of standardization continue in alliance with individual hospital and institution, initiative of preparing medical policy data at a national level will be accelerated.