The analysis and the design of turbojet engines are of great importance to the improvement of the system performance.Many researchers focus on these topics,and many important and interesting results have been obtained.In this paper,the thermodynamic cycle in a turbojet engine is analyzed with the entransy theory and the T-Q diagram.The ideal thermodynamic cycle in which there is no inner irreversibility is analyzed,as well as the influences from some inner irreversible factors,such as the heat transfer process,the change of the component of the working fluid and the viscosity of the working fluid.For the discussed cases,it is shown that larger entransy loss rate always results in larger output power,while smaller entropy generation rate does not always.The corresponding T-Q diagrams are also presented,with which the change tendencies of the entransy loss rate and the output power can be shown very intuitively.It is shown that the entransy theory is applicable for analyzing the inner irreversible thermodynamic cycles discussed in this paper.Compared with the concept of entropy generation,the concept of entransy loss and the corresponding T-Q diagram are more suitable for describing the change of the output power of the analyzed turbojet engine no matter if the inner irreversible factors are considered. The analysis and the design of turbojet engines are of great importance to the improvement of the system performance. Many researchers focus on these topics, and many important and interesting results have been obtained. In this paper, the thermodynamic cycle in a turbojet engine with the entransy theory and the TQ diagram. The ideal thermodynamic cycle in which there is no inner irreversibility is analyzed, as well as the influences from some inner irreversible factors, such as the heat transfer process, the change of the component of the working fluid and the viscosity of the working fluid. For the discussed cases, it is shown that larger entransy loss rate always results in larger output power, while smaller entropy generation rate does not always. The corresponding TQ diagrams are also presented, with which the change tendencies of the entransy loss rate and the output power can be shown very intuitively. It is shown that the entransy theory is applicable for analyzing the inner ir reversible thermodynamic cycles discussed in this paper. Compared with the concept of entropy generation, the concept of entransy loss and the corresponding TQ diagram are more suitable for describing the change of the output power of the analyzed turbojet engine no matter if the inner irreversible factors are considered.