As a key component of compound TBM, the rock-breaking effect of hob directly affects the construction efficiency and cost. Aiming at the problem of rock-breaking effect of TBM hob under sand and mudstone formation in Chongqing area, the mechanism of rock breaking by TBM hob is studied by numerical simulation and verified by practical application. Firstly, the material model parameters of hob and rock were determined by numerical simulation using ABAQUS software, and the model of hob and rock was constructed, and the analysis steps, contact and interaction were set. Secondly, the rock-breaking mechanism of hob was analyzed systematically. Finally, based on the Chongqing Metro Line 27 project, the application research of a new type of hob based on the mechanism of hob rock breaking was carried out. The results show that: The numerical simulation results are consistent with the prediction results based on CSM model, which verifies the accuracy of the numerical simulation results. It is revealed that the mechanism of hob rock breaking in Chongqing sand and mudstone formation is compression-shear failure. The rock-breaking effect of a new type of hob based on the mechanism of hob breaking is proved. The research results provide important theoretical basis and technical support for the selection and application of hob in shield construction in Chongqing sand and mudstone stratum, and have important significance for promoting the development of shield construction technology.