To investigate the crosswind environment and flutter performances of bridge deck with different wind barriers, a single-box-girder suspension bridge with the main span of 918 m was modeled by using the CFD. The wind speed profiles and crosswind reduction factors with types of wind barriers were compared. Then, the critical flutter wind speeds and three-component force coefficients with and without the superior wind barrier (elliptic-shaped) were tested in sectional model wind tunnel tests. The diverging mechanism for two kinds of sections was studied based on 2d-3DOF method. Results show that wind barriers could effectively change crosswind environment at the range of driving height by decreasing the mean speed. The rectangular wind barrier is the best choice to reduce crosswind speed, while the elliptic wind barrier performs acceptable effects and presents a smaller drag coefficient. According to the wind tunnel test, the elliptic-shaped wind barrier could make the drag coefficient much larger than the initial section, and the critical flutter wind speed increases mildly. The analysis results by 2d-3DOF method indicate that the diverging mechanism changes quite noticeably.