The invention relates to a plasma excitation source device, in particular, a plasma excitation source device of a high-power laser system. The plasma excitation source device is composed of a machine base, a cathode, a spiral flow guiding device and an anode assembly; the inner-layer wall body of the machine base form a cooling flow guide tube; the middle-layer wall body of the machine base form a cathode connecting rod; a space in the cooling flow guide tube forms a cooling water supply channel; a space between the outer wall of the cathode connecting rod and the outer-layer wall body of the machine base form an air chamber; thread pitch spaces of spiral flow guiding ribs in the spiral flow guiding device form spiral airflow channels; the anode assembly includes an anode sleeve and an anode, wherein the anode is embedded into the wall body of the anode sleeve; the cathode is connected with the front end of the cathode connecting rod of the machine base; the rear end of the spiral flow guiding device is installed on the outer-layer wall body of the machine base; the anode assembly is installed at the front end of the spiral flow guiding device; and the head of the cathode extends out from a space in an annular body structure of the anode. The plasma excitation source device of the invention can generate intensive arc light and high-energy electron beams and can be adopted as an excitation source of the high-power laser system, so that a laser can be high in power and simple in structure.