For the purpose of engineering application of High-Performance Lightweight Composite Bridge Decks，it was necessary to study the approximate calculation method of structural design indices. On the basis of finite element modeling，orthogonal tests were designed to obtain the key factors influencing the maximum tensile stress of UHPC，the ratio of local deflection on bridge deck，and shear stress of stud. The Latin hypercube sampling method was used to find out the internal relations between structural design indices and their key factors. Approximate calculation formulas of the maximum tensile stress of UHPC，the ratio of local deflection ，and shear stress of stud were presented，which were examined by statistical tests，judgments based engineering experiences- full-scale model tests and push-out model tests The results show that the linear correlations and regression effects of the formulas were significant，and the qualitative analysis were consistent with the general engineering experiences. The relative error between the calculated value of the three indexes and the measured value is less than 10%. They are of good applicability.