Abstract--Cloud service provider needs to meet the service requirements of cloud customer such as response time, scalability, high availability and mean number of tasks in the system. For this reason, the purpose of this paper is to analyze the performance of cloud computing center. We describe simulation model for performance evaluation of cloud server. Accurate estimation of the request response time and mean number of tasks in the systems is obtained using GPSS simulation language. The model allows cloud operators to determine the relationship between the number of servers and response time, mean number of tasks in the system.