The invention discloses an on-line monitoring method for cutter abrasion damage based on main shaft driving current and working step. The method is made by the following steps that realizing communication with a numerical control system to obtain machining working step information, meanwhile, the driving current and the load of the main shaft are monitored, and on the basis of a normal cutter andabrasion damage cutter cutting torque difference analysis and statistical quality control principle. Control graph for drawing average current / load required by each working step processing, a control graph control line is reasonably formulated, the abrasion state of each working step is judged, and a tool changing or cutter edge grinding rule is formulated. According to the variation of instantaneous main shaft current or instantaneous load with the deviation from the instantaneous current / load in normal machining in each working step of machining, the cutter breakage is determined, the alarm signal is sent to inform the numerical control system to emergency shutdown so as to avoid the serious consequences of damaging the workpiece and the machine tool. According to the method, on onehand, the part rejection rate and the machine tool fault rate can be reduced, on the other hand, the service life of the cutter can be prolonged to the maximum extent, and the use cost of a plant cutter is reduced.