The invention discloses an anti-collision method for a main shaft of a machining center. The anti-collision method for the main shaft of the machining center comprises the following steps that the origin offset N of an external workpiece of an axis Z is obtained, the coordinate value M of the axis Z of a current workpiece is obtained, the length X of a tool handle is obtained; and the maximum Z-direction feeding distance R of the main shaft is calculated according to the N, the M and the X, and T is assigned to the soft limit in the negative direction of a machine tool. According to the tool,when an operator forgets to set the tool, the tool is wrong, the tool clamping length is not enough, the tool length compensation error is avoided, and the program is wrong, an alarm is given out in advance, and therefore the colliding occurrence by the main shaft is avoided.