Ball mill filling rate measuring device

A ball mill filling rate measuring device disclosed by the present invention comprises a positioning detection structure, the positioning detection structure comprises a sliding sheath, the sliding sheath is internally provided with a protection structure, and the protection structure comprises a measuring slide scale. According to the ball mill filling rate measuring device, through the arrangement of an inner rotating air cavity and a connecting clamping rod, when a sliding sheath shrinks to the lower end of a front sliding clamping groove, air in the sliding sheath can be compressed through sealing between the lower end of a measuring sliding ruler and the interior of the sliding sheath, so that air flow enters the inner rotating air cavity from a bottom vent groove; and then the dust is sprayed out from the inclined air outlet, so that the dust at the lower end of the front sliding clamping groove is cleaned through blowing of the air flow, impurities are prevented from staying at the lower end of the fro