The invention discloses a large gear detecting method with high efficiency and high measurement accuracy, and a detecting device. The method adopts a coordinate method. A rotating device is used for rotating a detected gear; a length measuring device is used for detecting the toothed outline of the detected gear; the change of the relative position between a reference axial line of the detected gear and the length measuring device is determined by a laser tracker; and then the change value, the data collected by the length measuring device and the rotational angle data of the rotating device are processed so as to obtain geometric errors of the detected gear. The detecting device comprises the rotating device used for positioning the detected gear, the length measuring device used for detecting the toothed outline of the detected gear, and the laser tracker used for determining the change of the relative position between the reference axial line of the detected gear and the length measuring device. The invention innovatively combines the laser tracking technology with the large gear coordinate measurement, and realizes accurate and quick measurement to a plurality of errors of the large gear by using the coordinate method.