From the initial software production based on hand-made way to large-scale heterogeneous and distribution of software production, more and more people recognize that the core of improving software productivity and quality is the software process management. Thus, academia emerge a lot of research on the process of software in recent years. Mainly:Software process modeling and the establishment of the modeling language, Software process metrics, Software process formalization research, Software evolution research, Software process control and improvement and so on, achieving many progresses in these areas. Cloud computing is becoming a hot spot of academia and industry attention and research. However, many people are only concerned about model and algorithm implementation of cloud computing, rarely focus on cloud computing service process.Based on the view of "the process decide the product quality", in order to improve the efficiency of the implementation of the service process and improve service quality, make some research on Cloud computing service process model, formal modeling and service process metrics system in this paper.Firstly, we point out the definition of the different particle size of the service process with reference to the definition of software process. And give the system-level process model of cloud computing services process, the cloud computing early realization process, the cloud computing service process and the evolution of the cloud computing service in detail.Secondly, In order to more accurately describe the cloud computing service process, this paper formally defines the service process model based on the Weighted Petri Nets. Besides, the resource allocation algorithm of the service process is given.Finally, according to the above service process modeling method is put forward, further study the update operations of the cloud service process model based on the Weighted Petri Nets. In summary, this paper systematically studies the different granular service process of cloud computing and continues to research the modeling and improve operations of the cloud computing service process, thus not only laid the foundation for the simulation, control and automation implementation of the service process, but also to improve the quality of the cloud service and efficiency of the cloud computing service process is of great significance.