Abstract: An online precise control method for truncating parameters of microscale abrasive grains includes the steps of: (1) clamping an electrode and a diamond grinding wheel to form a discharge circuit, and communicating a workstation with a power supply and a controller of a numerical control machine tool; (2) feedback controlling movement parameters of the machine tool and parameters of the power supply according to pulse discharge parameters, controlling a discharge current and a discharge voltage, and calculating a number of rotations of the grinding wheel; (3) determining a maximum truncating area of a cutting edge and a maximum effective number of rotations of the grinding wheel according to grinding wheel parameters and pulse discharge parameters, and precisely controlling a truncating area of a cutting edge of abrasive grains online by the calculated number of rotations of the grinding wheel; and (4) after the calculated number of rotations of the grinding wheel reaches a target value, calculating a truncati