To improve test efficiency, a test instrument for coupling component in certain type airborne weapon control system is designed. According to the characteristic, relationship with input and output, and test principle of certain type airborne coupling component, a design frame of test instrument based on PC104 is presented. The core of the hardware is PC104, the modularized design is adopted in software design and the fault can be confirmed into test unit through exhaustive test. Pay more attention to analyze the realization of test instrument hardware, test process and method of fault diagnosis. The results demonstrate that the design can realize the test signal receiving and sending real time, improve test efficiency and reliability of instrument running.