The invention discloses a solid-liquid phase change heat exchange working medium for power generation by oceanic thermal energy, wherein a ternary solid-liquid phase change heat exchange working medium matrix mixing material is prepared by mixing n-pentadecane (C15H32), n-hexadecane (C16H34) and n-hexadecane (C17H36) at a weight ratio of 6:60:34, and a modifying material with high-thermal conductivity, namely expanded graphite, is added into the mixed material so as to intensify the heat conductive performance. A dispersant, namely organic bentonite, is added into and the dispersion stability of the organic bentonite is improved by ultrasonic oscillation. The solid-liquid phase change temperature range of the solid-liquid phase change heat exchange working medium disclosed by the invention is 14.5-17.5 DEG C, the phase change potential heat value of the working medium is about 212.1kJ/kg and the volume expansion ratio of the working medium is about 8.5%. The material serving as the solid-liquid phase change heat exchange working medium for power generation by oceanic thermal energy can satisfy the basic requirements on solid-liquid phase change heat exchange working medium for power generation by oceanic thermal energy.