Abstract: To optimize active heat storage system in solar greenhouse and screen for high-efficiency heat storage media, a comparative analysis was conducted to evaluate thermal storage performance of purified water, light-absorbing modified water, and carbon-based suspension media including bamboo charcoal powder, lampblack ink powder, and carbon nanotubes in solar greenhouse．By monitoring temperature at hourly intervals from sunrise to sunset, heat storage performance was characterized using metrics such as heat storage capacity during heating phase, heat release capacity during cooling phase, and heat retention efficiency to investigate photothermal conversion and heat release patterns of different carbon-based suspensions in solar greenhouse．Results indicated that all carbon-based suspensions exhibited performance metrics numerically superior to those of purified water．Among them, carbon nanotube suspension at a 5% concentration achieved a heat storage retention efficiency of 76.3%, demonstrating the best overall performance．Lampblack ink powder suspension at a 10% concentration exhibited the largest temperature rising amplitude, indicating excellent heating capacity．A comprehensive analysis revealed that carbon nanotube suspensions, under optimized concentrations, was a promising medium capable of effectively enhancing heat storage and thermal energy utilization efficiency．A theoretical basis in materials science was provided for energy-efficient design of solar greenhouse．