Abstract: The artificial ground freezing (AGF) has long used CaCl₂ brine as the cold transfer medium, but for the new requirements of underground engineering on the high strength and short duration of ground reinforcement, the traditional brine medium often fails to meet the new conditions, and deep freezing using an ultra-low temperature working medium as the cold transfer medium is theoretically considered to be an important direction for the AGF method to solve this problem. This paper completes the first in-situ test of liquid CO₂ medium with double-row freezing pipes based on self-developed new refrigeration equipment, and comprehensively analyzes the freezing effect and compares it with that of the traditional brine medium. The results show that: the temperature of the new cold transfer medium decreases very quickly, reaching -30 ℃ within 1 day of operation, and reaches below -40 ℃ in 3 days, and then gradually stabilizes. Local closure of the freezing wall takes only 3 days, and the formation of a continuous and reliable freezing wall takes only 7 days, saving more than 3 times the time compared with traditional brine freezing. In the whole process of freezing, the development rate of frozen soil of the new CO₂ medium is greater than that of brine freezing, and the longer the freezing time, the greater the increase, the rates on days 20, 30 and 40 increase by 31%, 35% and 40%, respectively. The freezing wall formed by the "plum-blossom" double-row pipes is roughly V-shaped, the frozen soil extends about 600 mm beyond the lower end of the freezing pipes in the vertical direction, and the total thickness of frozen soil reaches 3.06 m in the horizontal direction after 36 days of freezing, while the average temperature of the freezing wall drops to -20.1 ℃. In the insulation section near the ground surface, the freezing wall thickness on one side at the end of the test is 350 mm, compared with 1103 mm in the standard freezing section; the extension is reduced by about 2/3, and the soil temperature rises by more than 10 ℃; therefore, the outer wall insulation of the freezing pipe can effectively reduce the cold loss of the new cold transfer medium.