Abstract: Performance properties of an engine specify its performance and states.In the full life cycle of research,manufacture and operation of the engine, the performance properties which make the engine be in the state of maximal economic property are referred to as economic performance properties.Economic property of an engine not only incarnates in the develop stage but also in the full period of its develop and operation.From the point of view of improving economic property of engines,the analysis of engine properties is made in this paper.It is found that thermal efficiency is only an index to evaluate its economic property,but is unfitted to regard as a decision index for selecting economic performance properties of engines.For an engine of gas turbine,the economic optimization model is founded with the objective function of its life cycle cost,and the solution of the model is obtained by calculation.Through the comparison with the object function of thermal efficiency,the former can obtain economic performance properties of engines,whereas the latter cannot.It is emphasized in this paper that introducing the economic performance properties for developing engines,researching the methods and modes of determining the economic performance properties,and accumulating and collecting the information about the relationship between performance properties with costs are an important aspect of improving the performance of engines.