The method for testing critical region protection was studied. A method called SVAM (shared variable address monitor) for testing critical region protection mechanism of shared variable, which is based on monitoring shared date address, was presented. The proposed testing method consists of a real-time address monitor module and a shared variables address list. When the system is running, SVAM will monitor the variable written on the address bus. If the variable is updating and the interrupt is open, the system will enter uncontrollable status, and the critical region protection mechanism is corrupted. The correctness of SVAM was verified through theoretical analysis, and the validity of SVAM was verified through an embedded real-time operating system software testing project.