To solve some problems like the lacking test points and the low level of test coverage of the complex PCB,IEEE1149.1 was published and developed a new technology,namely boundary scan.Thetestablity system is based on boundary scan technology andconsists of the test software and the test controller and the targetcircuit board.At last, the test result which the testablity system did fault test of the unit under test(UUT) has indicated that the systemmeets design requirements of capture test and interconnection test, and has ability to diagnose and position bridge fault and stuckat fault.