Dynamic composing Web services provides an efficient mechanism to offer complex large systems. Substantial progress has already been made towards composing Web services. Unfortunately, these approaches cannot build a model of the whole life cycle of composed Web services. In order to solve this problem, we designed a model named Service-Cloud model based on the forming picture of clouds in nature. Service-Cloud model can describe the whole life cycle of the composed Web services: discovery, compose, publish, and terminate. Based on Service-Cloud model, we also designed and implemented a prototype