According to the problem of low fault isolation rate for single line replaceable unit (LRU) during test program set (TPS) testing of the equipment without special test interface, test signal parallel extraction technology is adopted. Test hardware such as test adaptation module of LRU is developed. The test signal from LRU is parallel extracted to automatic test equipment to perform test analysis, and signal LRU fault isolation is reliably realized, while the problem of test signal distortion from signal parallel is solved using dynamic library data analytic technology in test programs. And the accuracy of test signal parameter analytic is improved.