Abstract: The efficiency of ocean thermal energy conversion (OTEC) system is low due to the small temperature difference, so it is important to improve the efficiency of OTEC system. There are many factors affecting the OTEC system efficiency. The influence of thermodynamic cycle, heat transfer system of warm and cold water, turbine, working fluid pump, warm and cold seawater pumps and other power devices on the system efficiency was systematically analyzed in this paper. The research results showed that, the following approaches can be adopted to improve the efficiency of the OTEC system: non-azeotropic working fluid should be used to reduce the irreversible heat loss and then improved the OTEC efficiency in thermodynamic cycle; the heat energy in the thermal cycle system was recovered by intermediate regenerative extraction and cascade utilization of ammonia depletion solution, and the kinetic energy in the cycle was reused by turbine; the heat transfer temperature difference between warm and cold seawater and working fluid should be optimized to reduce the energy consumption of warm and cold seawater pump; the influence of the structural form of turbine, working fluid pump and warm and cold seawater pump on the efficiency should be considered; the organic seawater pipes with certain thermal insulation performance and low friction was recommended to use.