In this study, we developed an order communication system (OCS) gateway, which observe the protocol of HL7 standard and is operated on PC. In the aspect of architecture, the OCS gateway consists of three modules, which are message transmission/reception, data processing, and security. In the aspect of user interface, the OCS gateway consists of two main screens, which are order data management and message transmission. The main function of the OCS gateway is to convert the order records such as pharmacy, observation and diagnostic study, radiology, other diagnostic study, and treatment to a message, which observe the protocol that presented by HL7 standard, and transmit the message to other OCS gateway. To enforce the security of this gateway, we applied a hybrid security method using both Rivest-Shamir-Adleman (RSA) and Data Encryption Standard (DES). With the developed OCS gateway, different OCS systems in the inside and outside of the country can exchange their order data effectively and safely. Because it is developed for PC base Windows operating system, this gateway is more transplantable to the existing hospital information system (HIS) which is constructed on PC.