Abstract: A self-advancing tunneller used in the soil can march forward independently by the axial pull force resulted from spirals' rotation in soil. This paper aimed to solve the problem of self-advancing feasibility of the tunneller in various soil layer and spirals' ultimate pull. By means of theory of MohrCoulomb,the theoretical equation of ultimate pull provided by spirals' rotation in soil was deduced using integral analysis and making calculation by combining resistance equation. The results show that the selfadvancing tunneller can realize self-advancing in cohesive soil and in improved sandy soil.