In order to quantitatively study the stress and deformation mechanism of ultra-deep circular foundation pit， the finite element models of the operation process of ultra-deep circular foundation pit were established through Midas GTS. The stress and deformation of the enclosure structure and the surface settlement around the foundation pit are discussed and analyzed by altering the local weakening degree of the underground diaphragm wall, the number of the first and subsequent amplitudes of the underground diaphragm wall, the embedment depth, the inner diameter of the foundation pit, and other parameters. The analysis results show that: 1) The design of the envelope structure of this project has a certain optimization space; 2) The 8th ~ 10th ring beam is where the maximum horizontal deformation and stress of the envelope structure are concentrated; 3) With the increase of the degree and number of amplitudes weakening, the enclosure structure experiences an increase in deformation, and a decrease in stress. Similarly, the surface settlement around the foundation pit also increases with the increase of the degree of inter-amplitude weakening and amplitude number. The analysis results provide valuable references for the design and construction of similar ultra-deep circular foundation pits.