Abstract: In order to improve TBM tunnelling efficiency and reduce construction costs, it is necessary to study the efficiency of rock breaking in a joint rock mass. UDEC was adopted to perform research on the influence of joint spacing, joint inclination, cutter spacing and penetration on rock breaking efficiency. The results show that: 1) the trend of specific energy consumption decreasing with increasing confining pressure slows down when the joint inclination increases or decreases from 30° to 90° or from 30° to 0° , and the increase of confining pressure is adverse to rock breaking when the joint inclination is approaching 90° or 0°; 2) The smaller the joint spacing, the more obvious the influence of confining pressure on specific energy consumption. With an increase of joint spacing, the influence of confining pressure on specific energy consumption decreases until it has no effect; 3) When the joint inclination is around 0° , it is better to choose a small cutter spacing as long as it meets the requirements of installation; when the joint angle is around 30° , the specific energy consumption is the lowest if the cutter spacing is about 100 mm; when the joint inclination is around 60° , the specific energy consumption is the lowest if the cutter spacing is about 120mm; and 4) If cracks produced by two cutters are cutting through the joint rock mass, the rock breaking efficiency is best with small rock mass penetration.