Abstract: Truss string structure is applied more and more to platform canopy of railway stations．Taking truss string structure of Beijing North Railway Station for example,the relationship between mechanical behavior and structural parameters are researched,from which it has been found that vertical distance and axial stiffness of the cable can greatly improve the structural mechanical properties under dead-load．Compared to dead-load,truss string structure is more sensitive to wind-load,research show that structural wind-resistance performance can be optimized through changing the vector high,cable-vertical distance and sectional area,etc．Based on the results of the structural performance research,the optimization design method for truss string structure is proposed,and this method has been applied to the canopy of Beijing North Railway Station successfully．