The invention, which belongs to the field of plasma equipment, provides a plasma generator mainly comprising a cathode part, an arc striking part and an anode part. The arc striking part is arranged between the cathode part and the anode part and is used for triggering an electric arc between the anode part and the cathode part; the electric arc ionizes working gas to generate plasma; and the plasma is sprayed out through the anode part. The cathode part includes a cathode base and a cathode head; the base body of the cathode base includes a cooling channel; and the cathode head is connected with the base body. Cooling water is led into the cooling channel through a water inlet; one part of heat is taken away when the cooling water flows through the cathode head, so that the cathode head is cooled effectively and thus the service life of the cathode head is prolonged. In addition, the arc striking part is arranged between the cathode head and the anode body, so that the stability of the arc voltage is improved while the distance between the cathode and the anode is increased to improve the arc voltage.