This paper introduces an objective synoptic typing method which uses the routine historical synoptic data. Some circulation patterns associated with a weather phenomenon are empirically summed up at first, discriminant conditions and sequence for each pattern are then determined. On the above basis, historical samples for each pattern can be obtained and automatically objective typing of circulations completed with computers. This method is used to deovelop the winter regional precipitation forecast system of Weihai city. The system has many characteristics such as the precipitation circulation patterns have clear physical means, the discriminant conditions are practical, and the system is automatic. At last the importance of synoptic typing in the interpretation and utilization of numerical products and several relevant points for attention are discussed.