In order to meet the need of the embedded application specific microprocessors development and overcome some disadvantages of current microprocessor simulation tools, a new embedded microprocessor simulation tool — VCPU is introduced in the paper. Being different from other microprocessor simulation tools, VCPU is a flexible full-featured multi-level virtual prototyping. The designer can use VCPU to verify the embedded system, both hardware and software in the early design stage. Errors can be found and corrected before fabrication， thus the design cycle is reduced. VCPU has been used in embedded microprocessor development successfully.