Ocean thermal energy is clean and renewable. In recent years, many scholars have focused on improving the generation efficiency of the ocean thermal energy conversion system. To the best of our knowledge, the majority of the scholars focus on equipment improvement and working fluid optimization, and few study how to reduce the outlet temperature of cold-water pipes. This paper establishes a numerical model, which is solved by the finite volume method, to analyze the temperature distribution and heat transfer characteristics of cold-water pipes during pumping. The influence of cold-water pipe materials, wall thicknesses, flow rates, and insulation layer thicknesses on outlet temperature is explored. In addition, this paper qualitatively gives performance optimization recommendations based on technical and economic indicators. This study will be useful for the OTEC community.