As the complexity of high-performance microprocessors increases, functional verification becomes more and more important and emerges as the bottleneck of the design cycle. At present, verification based simulation is widely used. However, most of simulation tools are focus on design space explore or software development. They cannot provide the ability of verification for designs? HDL implement. In this paper, we present a full system simulation platform based on the virtual machine, which is called VMSIM. VMSIM can evaluate operating systems and applications on microprocessors? HDL implement and check execution results automatically. VMSIM emphasizes on the microprocessors? functional verification. VMSIM implements many abilities for functional verification, including configurable verification procedure, error tolerance and fast error reproducibility. We have evaluated VMSIM in functional verification of a microprocessor designed in our lab. It demonstrates VMSIM is an efficient functional verification platform for microprocessors.