Rain-wind induced vibration (RWIV) is a violent oscillation that appears on cable stayed bridge under rainy weather. Many researchers agree that the rivulets (specially the upper one) play an important role during the vibration. In present work, the upper rivulet’s effect is focused. A circular cylinder with an arches attachment on its surface is modeled to take the place of cable- rivulets system section in RWIV. Using finite volume method (FVM), 3D Flow past the cylinder-arch model is simulated for subcritical Reynolds Number (Re, ≈6.8×104). Large Eddy Simulation (LES) method is drawn in as a closure of turbulence model. The attachment locating at different positions are calculated. The results show many differences between cylinder-arch model and bare circular cylinder, including force coefficients change dramatically and velocity distributions in wake zone vary remarkably. Responses of cylinder-arch system driven by aerodynamic forces are also studied. Fourth order Runge-Kutta Method is introduced to solve second order ODEs that describe the vibration of cylinder model. The first four modal response are calculated and then added to analyze cable oscillating properties.