Abstract:  Risers are grouped in close proximity in engineering. The interference of two tandem arranged risers widely exists. The selfdeveloped solver viv-FOAM-SJTU is adopted for the prediction of the time-domain voxtex-induced vibration （VIV） response of deep-ocean risers. After the study of the benchmark case， the simulations of VIV of two tandem arranged risers with different spacings are carried out. The distance between two risers is changed from D to 4Dwhere D is the riser diameters. The results show that the distance between risers has little effect on the vibration mode. The VIV responses of the upstream riser with different spacing are fall dominated by the 4th mode， which is the same with the isolated riser. The VIV mode of the downstream riser is lower than the upstream one because of the interference between two risers. The responses of the downstream riser with different spacings are dominated by the 3rd mode. While， the distance between risers has a great impact on the trailing riser. With the increase of the distance， for the trailing riser， the weight of the 3rd mode decreases， and the weight of the 4th mode increases.