To study the mechanism of adjacent shield tunnel segment cracking induced by foundation pit excavation and crack distribution characteristics, this paper establishes the finite element model of the new foundation pit project around the existing subway shield tunnel with ABAQUS software. Based on the extended finite element theory, the paper analyzes the influences of the distance between the foundation pit and the tunnel, the excavation depth of the foundation pit, and the relative position between the foundation pit and the tunnel on the crack distribution of the shield tunnel segment. The results show that with the decrease of the distance between the foundation pit and the tunnel and the increase of the excavation depth of the foundation pit, the length and number of cracks of the shield tunnel segment are increasing, and the cracking area expands gradually. The shield tunnel segment cracking induced by foundation pit construction is more serious when the foundation pit is located above the shield tunnel, compared with that under other working conditions.