The invention provides a memory fault injection method and a simulator thereof for a software BIT. A hardware circuit board carrying out BIT software serves as a mock object of the simulator. An analog module for simulating normal functions of a memory, a fault modeling and model analysis module for establishing and analyzing fault sequence files, a fault injection module for matching the faults to be injected, and a fault behavior analog module and a peripheral cross-linking environment simulation module are added to the simulator. The method includes establishing a fault mode base, writing and analyzing extensive makeup language (XML) fault sequence files into identifiable fault sequences, searching and injecting corresponding faults when a processor accesses the memory, and performing fault simulation when the faults are triggered. According to the method and the simulator, the injected fault modes are complete and fully cover test cases under each fault occurrence for the memory, sufficient tests can be performed on the BIT software on a circuit board level, and only the BIT software after the sufficient tests can guarantee accuracy and timeliness of BIT fault prediction of aeronautical airborne equipment and further guarantee system reliability and safety.