Through definition of design service life for bridges and their elements,components classification according to structural systems,durability type research as well as investigations of their actual operating lives and recommended design service lives in specifications home and abroad,a direct method and also a simplified one were proposed to determine design service life of bridge structural elements based on the life-cycle cost analysis.As for direct method,element service life schemes were established,and then the one with optimal economy can be selected through life cycle cost calculation of each scheme.As for the simplified method,a calculation formula was presented for classification and evaluation of the influence coefficients and foundational design service lives of bridge elements were recommended based on professional investigations.Finally,a sea-crossing project was taken as an example to illustrate the process of design service life determination for bridge structural elements.