Abstract: The Full Face Hard Rock Tunnel Boring Machine (TBM) is widely used in the construction of tunnel engineering projects, and the stress of its hob in the process of rock breaking has always been the key problem in the design and construction stages of TBM. In order to study the stress of the hob in the process of TBM rock breaking, this paper simplifies the movement mode of the hob, comprehensively uses the shear and tension failure mechanism, respectively studies the stress of the hob when the hob rotates with the cutter head and when the hob moves in the approximate straight line in the heading direction, and deduces the calculation method of the normal force and rolling force of the hob in the process of rock breaking without considering the influence of the rotation of the hob itself. The main influence factors of normal thrust of hob are further analyzed to ensure the rationality of parameters of calculation model. The model is applied to an actual engineering case, and compared with the field monitoring results and the CSM model calculation results of rock breaking force of approximate constant cross-section disc hob. The results show that the calculation results of the model and the field monitoring results are in good agreement, and the calculation error is smaller than that of the CSM model of rock breaking force of approximate constant cross-section disc hob, so as to verify the model. The applicability and rationality of the proposed method provide a reference for the mechanical calculation and model study of TBM hob rock breaking and its application in related projects.