In the paper, the qualifications for the breaking of the boulders directly by shield machines are studied by means of analysis on the boulder/soil mechanics. The research results show that the larger the diameters and overburdens of the boulders, the easier the boulders can be broken by shield machines; the smaller the difference between the strength of the boulders and that of the surrounding soils, the easier the boulders can be broken by shield machines. Furthermore, the method for the coping of the boulders that can not be broken directly by shield machines is presented in the paper with project cases.