Abstract: To investigate the wind-resistant behaviour of a two-column tower, the CFD numerical simulation was adopted to analyze the unsteady flow around two rectangle columns with round corner in tandem arrangement according to an actual bridge tower. The effect of wind velocity, wind direction and spacing ratio on aerodynamic coefficients of the tower cross section were analyzed after checking the reliability of the analysis method, and the vortex-induced vibration of each column and the whole tower were further explored. Moreover, the magnitude and the change trend of lateral force of upstream and downstream column were compared to study their effect on the increase of tower torsional moment. The results show that aerodynamic characteristics of tower columns in tandem arrangement are significantly affected by the spacing ratio and the critical value is about 3, where the sum of drag coefficient of each column is the minimum and the root mean square value of lateral coefficient is close to 0.