Abstract: According to military standards and other materials, this paper introduces and analyses a new kind of aircraft testtechnique---low level coupling (LLC) test approach. The advantages of the LLC test approach are the relative low cost, portabilityand availability of test facilities and potential for reduced live aircraft testing. So, the LLC test approach is widely used in aircraftlightning indirect test and aircraft high intensity radiated field (HIRF) test. Aircraft lightning indirect test is used to determine thetransient levels in individual conductor open circuit voltages, short circuit currents and wire bundle induced currents, aircraft HIRFLLC test is used to determine the transfer functions and attenuation curves.