Abstract: A positive high-voltage laser having a super-long discharge tube, including a gas storage tube having two ends respectively provided with a reflecting mirror and a light emitting surface; a water cooling tube in the gas storage tube; and a discharge tube inside the water cooling tube having two ends, each provided with an electrode. A liquid circulation space is between the discharge tube and the water cooling tube, and the water cooling tube extends outside the gas storage tube by water inlet and outlet tubes. A cathode is in a cathode chamber at the end of the discharge tube closest to the light emitting surface; a spiral gas return tube communicates with the cathode chamber; an anode circumscribes the outside of the water cooling tube at the other end of the discharge tube. The positive high-voltage laser can increase power with a limited length.