USM(Unit Service Management System) is the development tool and methodology to handling the event process in a U-City integrated platform by using the minimum unit services. USM can be one of the SOA development methodology. Minimum unit service has a minimum business logic that can be executed with input and output parameters. Minimum unit service consists of three parts : service profile, service input and output parameters and service execution information. USM provides two types of the execution method. One is module execution and the other is web service execution. The development of the event sinario by the USM development methodology can reduce the cost and duration of the u-service development by raising the rate of reusing minimum unit service.