An energy-saving temperature difference energy-driven ocean profile dynamic system includes: a phase change chamber (1); a phase change hydraulic oil sac (3) disposed in the phase change chamber (1); an accumulator (16) connected with the phase change hydraulic oil sac (3) through an oil outlet passage (20); an external oil sac (10) connected with the accumulator (16) through an oil inlet passage (17); and an internal oil sac (8) connected with the external oil sac (10) through a first oil return passage. The phase change hydraulic oil sac (3) is simultaneously connected with the internal oil sac (8) through a second oil return passage. The external oil sac (10) and the phase change chamber (1) are disposed outside a sealed chamber, and the remaining components and oil passages are all disposed inside the sealed chamber. The system does not require a solenoid valve for performing control, thereby saving electrical energy. The system is able to float and sink on its own by means of the temperature difference in the sea water. Specifically, the system is capable of adaptively modifying the time for phase change according to the sea water temperature, and immediately floating or sinking after accomplishing phase change, such that the number of profile movements can be greatly enhanced. The system controls all the oil pressures directly from the hydraulic passages, and does not employ a conventional pressure sensor, such that costs are reduced and the reliability of the system is enhanced.