An improved computational method for buffeting forces of long span bridges, which substitutes the traditional wind tunnel test with the bridge segment model for CFD method, is proposed. In the case study of Tsing Ma Bridge, the pressure distribution induced by the wind field of the bridge decks was simulated. The nodal buffeting forces were computed and the local stress responses were obtained according to the CFD simulation and the refined finite element model. Preparation for buffeting induced fatigue analysis of bridges and structural health monitoring are provided.