The present disclosure provides an ion mobility spectrometer, which comprises: a power supply circuit, configured to provide a power supply voltage; a corona discharge configured to generate ions to be subjected to measurement, through corona discharge; an ion migration circuit configured to control migration of the ions; a migration zone structure configured to realize, under control of the ion migration circuit, mobility spectrum measurement of the ions which pass through the migration zone structure; a redundant charge extraction electrode arranged between the corona discharge structure and the migration zone structure, so that the ions which are generated by the corona discharge structure can pass therethrough to reach the migration zone structure; and a redundant charge extraction circuit, wherein the redundant charge extraction electrode is connected to the ground through the redundant charge extraction circuit.