Abstract: Gateway design is crucial for developing a GPS/GSM supervisory system with satisfactory system performance, availability and expandability. Several related key techniques for gateway design were dealt with. After analyzing different Short Message Service Center (SMSC) interface protocols, a protocol manager was introduced to achieve multi-protocol capability. Custom communication instruction format was proposed. The address conversion procedure was discussed in detail. Advantages of multi-thread and message driving in software architecture were also presented. The reliability of the gateway design strategy was proved by a practical implementation with the proposed techniques.