This study proposes a novel extraction–ejection combined power and refrigeration cycle for ocean thermal energy conversion (OTEC). Ammonia-water is utilized as the working fluid. By introducing a steam-turbine extraction-gas-driven ejector between the evaporator and the absorber, the gas flows into the absorber after it is cooled, thereby enabling the cycle to recover pressure-difference energy and produce both power and cooling outputs. A mathematical model is established for the energy and exergy analyses, and a genetic-algorithm-based optimal design was developed to determine the maximum exergy efficiency. Furthermore, a comparative study of traditional OTEC cycles is conducted. The results showed that at seawater temperatures of 30 °C and 5 °C, the refrigeration temperature reached −20 °C. Although the power efficiency of the proposed cycle was 0.85%, which is 3% lower than that of the traditional OTEC power cycles, the coefficient of performance and comprehensive efficiency, which represents the utilisation of exergy, reached up to 29.10% and 66.14%, respectively, which indicates its high energy utilisation performance. This novel cycle shows potential for OTEC, as it can satisfy both electricity and refrigeration demands.