The cutter was simplified to a vertical over-hung rotor-bearing system. The slant crack was set near the junction of shaft and disk, only considering two nonlinear factors: the slant crack and the nonlinear cutting force. 3-DOF dynamic equations of the system were founded. Based on this model, a stiffness calculation model of opening slant crack was chosen and the dynamic characteristics of slant cracked cutter were investigated by numerical simulation. The results showed that, when the system was under the action of crack, the orbit of the shaft center and frequency components of the cutter were significantly different from that without the crack. When n was 800 r/min, as the crack depth increased, the shapes of orbit of the shaft center varied comparatively great and the corresponding displacement amplitudes tended to increase.