A device sod a method for measuring servo gear idle position are provided. The method includes: outputting a start-up fixed force of a first rotation direction to an output shall of a servo under test, and recording a value of a start-up position of the output shaft when a position of a rotor of the servo under test changes for the first time; outputting a counterrotation force of a second rotation direction for rotating the output shaft to the output shaft, and recording a value of an counterrotation position of the output shaft when the rotor is in a stop status after a predetermined interval; and calculating a value of a servo gear idle position in a current measuring point, the value of the idle position is the absolute value of the difference between the value of the start-up position and the value of the counterrotation position.