UML has become a standard language for designing software systems. To help software developers design a correct UML model for a software system has become an important goal for many UML CASE tools. We propose a new UML virtual machine based on abstract state machines. We combine the UML meta-model, UML model and user objects model into one under the ASM virtual machine for UML. Since the ASM virtual machine for UML supports OCL, software developers can precisely design a software model and then find some errors such as inconsistency in the model with the help of the ASM virtual machine.