The invention relates to the field of motor rotor assembly, and discloses an automatic discharge device. A divider drives a dividing plate to rotate to a discharge procedure in an indexing manner; a direction device is pressed into a rotor pickup manipulator on a bracket to pick up the assembled rotor and to clamp a shaft in the rotor; the rotor pickup manipulator moves the rotor to a rotor turnover mechanism; the rotor turnover mechanism clamps the rotor and turns over 90 degrees to horizontally put the rotor; a rotor clamping and moving mechanism clamps the horizontally put rotor and/or vertically moves to an inlet of a guide rail mechanism; when an import driver drives a fan-shaped block to move downwards, a guide plate tilts upwards and prevents the rotor from sliding into a ramp rail; and when the import driver drives the fan-shaped block to move upwards, the guide plate is put on the bottom surface of the inner side at the inlet of the ramp rail and assists the rotor in sliding into the ramp rail, an importer imports the rotor into the ramp rail and the rotor rolls out through the ramp rail. The automatic discharge device is fast in production cycle, high in production efficiency and low in production cost.