Abstract: In artificial ground freezing construction, traditional low-temperature coolants are limited by low freezing efficiency and high energy consumption, making it difficult to meet the technical demands of complex strata. To address these challenges, this paper innovatively proposes a novel ground freezing technology based on liquid CO₂. This technology utilizes three closed-loop circulation systems to efficiently transfer ground heat and achieve rapid freezing. Through in-situ freezing tests and numerical simulations, the freezing reinforcement effect and temperature field evolution characteristics of liquid CO₂ coolant were systematically analyzed. Experimental results show that the cooling rate of this new technology is three times higher than that of conventional brine coolant. After one day of freezing, the soil temperature rapidly drops to -30 °C, and after 36 days, the frozen wall thickness reaches 3.06 m, with an average temperature of -23.9 °C and a frozen wall expansion rate of 33.6 mm/d. These results are significantly superior to the requirements of current brine freezing standards, and demonstrate excellent impermeability and structural stability. Based on a coupled hydrothermal model, the process of frozen wall expansion and soil ring closure was further revealed: the frozen wall temperature decreases in a stepwise manner over time, and ring closure between adjacent freeze pipes can be achieved in approximately five days. Compared to traditional brine coolants, the liquid CO₂ technology, with its rapid phase change latent heat release and efficient cold transfer, significantly improves freezing efficiency and reduces construction costs.