Abstract: A 3-D mesoscale operational numerical model system (MOMS) is developed on a microcomputer PC-386 according to the requirements of real-time operational forecast and data availability. The system including data input, objective analysis, forecast processing and results output is run automatically. It can provide prognosis and precipitation forecast at any given interval within 24-hour period. The results are displayed on terminal with color graphics. The system was in operation in the summer experiments of Beijing-Tianjing-Hebei mesoscale experimental base during 1989 to 1990, and provided numerical forecast product services during the period of 11th Asian Games. The experimental operational forecast with this system was also carried out in weather forecast stations of Inner Mongolia Autonomous Region and Hebei Province in 1990. The results show that the model system operates steadily and can meet, with regard to timelyness, the requirements of real-time operational forecast. The forecasts provided by the system contribute positively to making 12－24 hours short range forecast