Abstract: There are three important shortages having influence on engineering application in crack initiation approach of durability analysis established.They are researched and improved in this paper.Durability test for a group of analogous specimens is carried out under service load spectrum of the structure.On the basis of test data of crack initial life,the factors c_p in three-parameter formula of crack initial p-s-N curves for structural details are determined by backward compute method. After analyzing big influence of standard deviation of logarithm crack initial life on economic life,this standard deviation is made as 0.176~0.2 that is general value for logarithm fatigue life of aircraft structures. Then an improved crack initiation approach of durability analysis is developed and is successfully applied for the durability evaluation of aircraft structures.