The paper begms with the statistical data of service year of the aucraft withdrawn from our wilitary service. Using for reference the working condition of several types of forelgn fight-aircraft , the aircraft 's natural life , technical life and economical life are put forward , so the aircraft 's service year can be determmed reasonably. And the prolongation of the economicallife is also analysed mathematiclly. It is pomted out that under the clrcumstances of the renewal speed of the airbone equipment being more faster than that of the aircraft platform , the prolongation of the aircraft's service life may be an appropnate way to achieve "less investment. higher efficiency" in the equipment developing