Cold-water pipe (CWP) is one of the most novel and challenging devices in the Ocean Thermal Energy Conversion (OTEC) floating structure. When the internal fluid velocity inside the pipe exceeds a certain critical velocity, the CWP may cause flutter or divergence. In this paper, numerical model is developed to study the stability characteristics of CWP with internal flow. First, linear motion equation for small lateral motions of CWP is derived using the Newtonian analytical approach, and then the motion equation is solved by Galerkin method in order to determine its stability characteristics. The numerical study was conducted to investigate the effects of axial flow velocity ratio, velocity angle ratio, and tangential velocity ratio on the dynamic response of CWP aspirating fluid. It was found that tangential velocity ratio ϕ=0 cannot effectively explain the Kuiper' experimental phenomenon that the negative pressurization has little effect on the dynamic instability of the pipe. And the axial velocity ratio and velocity angle ratio have significant impact on the stability of the CWP. Inversely, ϕ ≠ 0 can explain experimental phenomenon of Kuiper, and the impact of axial velocity ratio have marginal impact on the stability of the CWP.