Abstract: The mathematical model of the gas turbine performance in the condition of fault was established by using the thrust work potential transfer function,which is a figure of merit of the work potential based on the second law of thermodynamics.The performance matrix of fault model was derived by using the small deviation method.The thrust work potential transfer function was compared with the efficiency,which was the traditional function.The thrust work potential transfer function among the components was compared.The thrust work potential transfer function of the gas turbine system was analyzed.The results show that the thrust work potential transfer function can express the gas turbine performance wonderfully in the point of view of transferring the work potential contained in fuel into useful thrust work.This lays a foundation for the future study of the capability of the gas turbine under the conditions of all kinds of faults.