The noninterference concept for actions of system to information domains is proposed. On the basis of this concept, the noninterference model is extended to nondeterministic systems. The noninterference concept based on actions of system simplifies the “purge” of the action sequence of the system. As a result, this model has concise unwinding conditions which are easy to understand and use. The extended model can be used to verify not only static but also dynamic information flow policies. Finally, a dynamic label based access control model is designed, in which the concrete semantic of the actions such as read, write and execute are defined, and its security is verified by the noninterference model.