In order to deduce the calculation method for the cutting tractive force and for the cutting torque, the author uses rock strength limit as material constant and relies on the actual state of the rolling cutting in TBM boring and the mechanism of the crushed rock falling along the weak area on both sides of the cutting edge. The author makes comparison and contrast between the calculation results and the actual boring records. In the whole deduction process, the author takes the loading conditions of the rock into consideration only.