In order to explore the partial discharge characteristic of cavities in insulation of mining ethylene propylene diene monomer (EPDM) cables, EPDM samples with two types of defects, namely dielectrically bounded cavities and electrode bounded cavities, were made.Then, on a partial discharge measurement system, the partial discharge experiments were conducted at sinusoidal voltage with different frequency.The partial discharge inception electric field, inception partial discharge amplitude and partial discharge distribution were measured.The results indicate that the inception electric field of partial discharge from cavities depended on the frequency of applied voltage and cavity's diameter.The partial discharge distribution of two types of cavity was different at different voltage amplitude.The results provides a basis for diagnosing the cavity's type and the development of partial discharge in mining EPDM cables.