Based on the related knowledge of the functional disassemble in the engneering design. The feedback signal is thought to be classed as positive, zero, negative signal at the port of input by analyszing the working principles and its functional role model construction of feedback system. Then, the technology of the fault transmit analysis about feedback is put forth. The process of the fault analysis is illustrated by the fuel-metering system of the jet plane engine. The research results show this method can resolve a type of fault analysis of the feedback system effectively, and the range of applications of the functional role model is extended along with it.