Focused on the demands of highway weather forecasting and early warning along the highway, an automatic observing system, the Road Weather Information System (RWIS), is designed, which adopts the technical specifications according with routine meteorological observation and the requirements of highway weather observation for timeliness and reliability are also taken into account. Compared with the routine meteorological observation, the design of RWIS has the following characteristics: the adaptation to field unmanned detection environment, observation elements selected on needs, modularization design for flexible configuration, sensor layout with special requirements, and the compatibility and parallel of data flow, status flow, and control flow. The hardware structure of RWIS uses the modularized design of integrating all kinds of sensors. The communication transmission uses the data object dictionary approach to organize meteorological observation data and equipment status information, and uploads in realtime by data flow, which are analyzed and managed by acquisition software and central software. The system has been applied presently nationwide and the collected data have been uploaded to CMA to be used in the operational system platform. The observation products distributed by the CMACast system have been shared and applied nationwide.