Carbon dioxide phase change fracturing technology is a brand-new and efficient cracking and tunneling technology. Because the method utilizes the change of carbon dioxide state, it belongs to a pure physical process. By adjusting the release rate of gaseous substances, it can effectively control the pressure of the gas, and achieve micro vibration, zero flying stone, zero toxic gas emission, and no micro harmful effect of shock wave, but the application of carbon dioxide phase change cracking technology in urban foundation pit excavation is less. In this paper, through the analysis of three different cracking parameters of urban foundation pit excavation process, it is found that when the diameter of the cracked pipe is 85 mm, the construction safety can be guaranteed. In addition, according to the on-site cracking effect, the carbon dioxide phase change cracking technology is a safe, reliable, relatively economical and efficient excavation technology under urban complex environmental conditions, and will not affect the surrounding environment during use, but Its cracking efficiency has a great relationship with the air surface. [ABSTRACT FROM AUTHOR]