In this paper,the reliable performance and design expression of a cross-sea multi-span continuous rigid frame bridge are investigated under the combined effect of the wind-wave and the adverse effect of the vehicle.Then,based on the stochastic theory,the vehicle,wind and wave actions on the cross-sea continuous rigid frame bridge are simplified as a Poisson process,and are further assumed as a FBC process when the Ferry Borges-Cas- tanheta (FBC) method is adopted.All the wind,wave and vehicle actions are considered to be in extreme cases,and when the wind and wave actions are combined，their correlation is also taken into account.Moreover,the ex- treme nature of the vehicle is reflected in the load layout rather than in the load value.In order to determine the de- sign expression of the cross-sea continuous rigid frame bridge under the extreme wind-wave effect,the Monte-Carlo method,which is simple and mainly dependent on the computer data processing,is adopted to perform a simula- tion.Finally,according to the principle of keeping the sum of the squares of the differences between the structural reliability indexes and the target reliability indexes to a minimum,the optimal design partial safety factor is obtained.