Aimed at the problem of fatigue test to prolong life for aging aircraft, the method of determining fatigue test period to prolong fatigue(durability) life for old aircraft is put forward. The three different conditions were analyzed for choosing the fatigue test loadings; Based on the actual flying hours, the total equivalent flying hours were calculated by damage equivalency principle for service aircraft; The fatigue scatter factor of residual fatigue life was analyzed by numerical simulation based on fatigue life distribution, and the fatigue test period for aging aircraft was determined; Finally, this method was illuminated by a calculation example.