In order to research the effect of different cutting orders on breaking mechanism of TBM cutters for the rock without joints, this paper established the simulation models of breaking rock three TBM cutters in simultaneous and sequential orders, which is based on the 2D discrete element method. A series of numerical experiments were designed and the whole process of production and propagation of crack and rock breaking was successfully simulated. The simulation results showed that the cutter order determines the breaking mode, which is carefully analyzed: The chipping stress under the sequential order is higher than simultaneous way. The chips are formed by the side cracks under the two loading modes, while the shape of the rock chip are different. The distribution of the principal stress contour is almost symmetrical in different cutting order. Finally, conclusions and future work are summarized.