The invention discloses a cooling method and a cooling device for a semi-conductor side pump laser device. The semi-conductor side pump laser device comprises a laser cavity and a laser crystal bar which is arranged in the laser cavity, and according to the laser cavity, a plurality of rows of semi-conductor bar strips are adopted to carry out pumping on the laser crystal bar. The method comprises the following steps that a plurality of atomizing devices are arranged on the cavity wall of the laser cavity, and the atomizing devices are used for spraying water mist towards the laser crystal bar; and an air inlet as well as an air outlet are arranged in the direction parallel to the laser crystal bar in the laser cavity, and the air flow in the laser cavity is enabled to flow from the air inlet to the air outlet. The invention provides a novel composite cooling method and a cooling device with a compact structure and a good cooling effect, so that the effect of carrying out cooling on the semi-conductor side pump laser device which can not be cooled by water in the situation of high injected power is successfully realized.