A power tool, comprising: an electric motor comprising multi-phase windings; and a control circuit for controlling the electric motor to rotate; wherein the control circuit comprises: a driver circuit comprising a plurality of switching elements (Q1, Q2, Q3, Q4, Q5, Q6) having a plurality of driving states to drive the electric motor to rotate; a parameter detection module for detecting an electrical parameter of the control circuit; and a controller for outputting a pulse-width modulation control signal to control the driver circuit to change the plurality of driving states; characterized in that the electrical parameter comprises a bus voltage of the control circuit; and the controller is configured: to change an absolute value ( |ΔPWM|) of a variation of a duty cycle of the PWM control signal according to the electrical parameter to control a steady-state error of speed of the electric motor running in a constant speed to be within a preset range; to decrease the absolute value of said variation of the duty cycle when the bus voltage increases; and to increase the absolute value of said variation of the duty cycle when the bus voltage decreases; wherein an average inductance of each phase winding of said multi-phase windings is greater than or equal to 0.9 mH. an electric motor comprising multi-phase windings; and a control circuit for controlling the electric motor to rotate; wherein the control circuit comprises: a driver circuit comprising a plurality of switching elements (Q1, Q2, Q3, Q4, Q5, Q6) having a plurality of driving states to drive the electric motor to rotate; a parameter detection module for detecting an electrical parameter of the control circuit; and a controller for outputting a pulse-width modulation control signal to control the driver circuit to change the plurality of driving states; a driver circuit comprising a plurality of switching elements (Q1, Q2, Q3, Q4, Q5, Q6) having a plurality of driving states to drive the electric motor to rotate; a parameter detection module for detecting an electrical parameter of the control circuit; and a controller for outputting a pulse-width modulation control signal to control the driver circuit to change the plurality of driving states; characterized in that the electrical parameter comprises a bus voltage of the control circuit; and the controller is configured: to change an absolute value ( |ΔPWM|) of a variation of a duty cycle of the PWM control signal according to the electrical parameter to control a steady-state error of speed of the electric motor running in a constant speed to be within a preset range; to decrease the absolute value of said variation of the duty cycle when the bus voltage increases; and to increase the absolute value of said variation of the duty cycle when the bus voltage decreases; wherein an average inductance of each phase winding of said multi-phase windings is greater than or equal to 0.9 mH. to change an absolute value ( |ΔPWM|) of a variation of a duty cycle of the PWM control signal according to the electrical parameter to control a steady-state error of speed of the electric motor running in a constant speed to be within a preset range; to decrease the absolute value of said variation of the duty cycle when the bus voltage increases; and to increase the absolute value of said variation of the duty cycle when the bus voltage decreases; wherein an average inductance of each phase winding of said multi-phase windings is greater than or equal to 0.9 mH.