The vortex-induced vibration of a circular cylinder under pulsating flow was simulated numerically using Ansys software. The beat phenomena were caught and effects of pulsating frequency and pulsating amplitude on vortex-induced vibration were discussed. Results indicated that as the pulsation frequency increases from 0.2 Hz to 0.4 Hz, the multi-frequency phenomenon of cross-flow displacement was obvious, and the trajectory of the cylinder gradually became axisymmetric. As the pulsation amplitude increased from 0.2 to 0.4, the transverse flow amplitude increases significantly from 0.035 to 0.04. and its motion trajectory became more complex. In addition, the lift coefficient and drag coefficient increase by a maximum of 75.14% and 58.70%, respectively. It also provided a basis for vortex-induced vibration of offshore engineering equipment.