The actual drilling riser system usually is installed with six auxiliary pipes.Recent studies have shown that the pipes have a certain flow control effect on the mainline.Whether it has vortex-induced vibration (VIV) suppression effect needs to be studied, so a numerical simulation study for this problem was carried out.Based on the Reynolds-averaged Navier-Stokes（RANS）  equations, combined with the k-ω turbulence model, the OpenFOAM solver of the embedded multi-cylinder motion solving module was used to get the computational fluid dynamics（CFD）solution of the incompressible fluid,and then the structural dynamics model was used coupledly to solve the fluid-structure interaction.The research focused on an oscillating drilling riser system at Reynolds number 20 000-85 000, typical reduced velocity 3-12 and angle of attack 0°-330°.The results show that the pipes have a suppression effect on the VIV of the drilling riser in general, and the effect is related closely to the incoming angle of attack and the reduced velocity.It shows the best suppression effect when the angle of attack is 210°and 330°.When the cross-flow VIV is relatively severe, the power spectrum has a unique peak frequency.The main frequency is close to the natural frequency of the riser system.The VIV orbit trajectory of the riser system has various shapes, such as raindrop orbit, inclined inverted raindrop orbit, inclined asymmetric “8” orbit and sub-oval shaped orbit.