Abstract: In order to resolve the problems of automatic test system (ATS) self-test difficulty and under test unit (UUT) fault detection, prognostic and health management, remote monitor and diagnose system based on distributed network is studied. The system can do remote test, online monitor, fault detect to ATS and UUT with remote information and test data based on fault tree and expert experience, which can reduce fault probability, fasten the speed of outfield response and direct the worker to remove the fault and maintain the ATS and UUT.