This research work investigates the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. A riser made of Glass-fiber Reinforced Plastic (GRP) is used for this study. The mathematical model is derived based on Hamilton's principle and modeled by using a finite-element method. The riser is subjected to sea wave and current and the hydrodynamic forces are calculated using Morison's equation. A direct integration method namely Newmark integration scheme is proposed to solve the equation of motion. A MATLAB program code was developed to obtain the simulation results. The model used is validated by comparing the results with the analytical method and it shows a very good agreement. The simulation results are obtained to illustrate the dynamic characteristic of GRP pipe when subjected to combined sea wave and current. The effect of vortex shedding frequency and internal flow velocity on the response of riser are investigated and discussed in this study. © 2013 Asian Network for Scientific Information.