Abstract: Aiming at the problems of high dependence on grid power and poor off-grid endurance in field environments of traditional portable cold-hot compress devices, as well as the low accuracy of manual parameter tuning and obvious temperature fluctuation under variable temperature conditions of conventional PID controllers, this paper designs a four-stage multi-source complementary power supply system integrating photovoltaic power generation, hand-crank emergency power generation, vehicle-mounted power supply and lithium battery energy storage. Combined with semiconductor refrigeration technology, a temperature control scheme of variable universe fuzzy PID optimized by Particle Swarm Optimization (PSO) is proposed. MATLAB is used to carry out simulations of the temperature control algorithm and energy time-series operation, and Simulink is adopted to establish the model of power conversion circuits. Prototype tests are conducted under three typical ambient temperatures of 5 ℃, 24 ℃ and 38 ℃ for verification. The results show that the PSO-optimized controller reduces the temperature fluctuation of the device from ±0.1 ℃ to within ±0.06 ℃, and the total energy consumption of the whole machine decreases by 26.3% compared with the traditional PID scheme; the average error between simulated and measured temperatures is less than 0.35 ℃; the proportion of photovoltaic power output exceeds 65% in the daytime and reaches 76.3% throughout the day, enabling continuous 24-hour off-grid autonomous operation. This device is suitable for scenarios such as field emergency rescue, primary medical care and sports rehabilitation, and can provide quantitative basis and technical reference for the research and development of green portable medical and therapeutic equipment.