Abstract: In this paper,the quantitative fractography analysis model and means of metal structure materials are introduced,including the Paris formula,the trapezium method and the models based macroscopic characteristics of fracture surface.The using precondition of every model is also introduced.The fatigue expanding life of the fracture surface of 7B04 aluminum alloy and TA15 titanium alloy was calculated using Paris formula and trapezium method.The calculating results were compared and analyzed.Combing with the essence of trapezium method,the precondition and improving measure of trapezium method were proposed.When the beginning expanding crack size (a0) is more than the crack length of the first measurement station (a1),or the a1 is nearby the a0,the trapezium method is not necessary to be modified,but when a0 is shorter than a1,the trapezium method is needed to be modified during calculating the fatigue life between a0 and a1,i.e.,the trapezium method formula does not need to be divided by 2.The trapezium method formula keeps its primary form when calculating the life after a1.The calculating results using improved trapezium method show that the improved measure is reasonable.