Abstract: Based on Biolley‘s wake oscillator model, the differential equation for the response of the vortex-induced vibrations(VIV)of the riser is derived. The effect of the internal flowing fluid and the external marine environmental condition are taken into account. The effect of the internal flowing fluid on the response of VIV of the riser is studied using finite-element method. The fatigue life of the marine riser is analyzed by Miner's theory. The effect of the internal flow velocity on the response of VIV and the fatigue life of the riser is analyzed. Results show that when the natural frequency of the riser is near the vortex shedding frequency due to the change of initial velocity, the response of the VIV will increase and the fatigue life of the riser will decrease greatly.