Abstract: Rain-wind-induced Vibration (RWIV) appearing on cable stayed bridges involves complicated fluid and structure interactions and its mechanism is not fully understood. It is believed that the upper-rivulet which is often seen when the RWIV occurs plays an important role. In this study, the effects of the upper rivulet to the aerodynamic forces on the cable and flow pattern around it were numerically investigated. Different azimuths of the attached upper rivulet ranged from 0 to 60° were involved. The result showed that as the rivulet located at different position the boundary layer changed a lot and the forces on the cable and the flow patterns of the wake behind the cable were so that changed.