A plasma pyrolysis device of a telescopic striking arc relates to a plasma device and comprises a first electrode, a first electrode seat, an enclosure body, a second electrode, a third electrode, a second electrode seat and an electromagnetic driving assembly, wherein the first electrode is arranged on a notch of the first electrode seat, the first electrode seat is connected to the third electrode by the enclosure body, the third electrode is connected onto the second electrode seat by an insulation connection element, the second electrode is arranged on the second electrode seat and passes through a space in a ring of the third electrode to enter an inner space of the enclosure body, a space between a rod body of the second electrode and an annular wall body of the third electrode form an ionized gas passage, and the inner space of the enclosure body forms a plasma generation chamber. With the measure of the telescopic striking arc, the spatial distance between two main electrodes can be prolonged, and the energy of a high-temperature plasma arc is increased; with the arrangement of an electromagnetic coil and the arrangement of magnetic beads in a driving rod at intervals, the arc striking electrode is driven; and the plasma pyrolysis device is simple and reasonable and is reliable in working.