The invention provides a longitudinal cooler system for laser crystal. An upper cover plate layer, a heat dissipation layer, a small-hole water diversion plate layer, a width water diversion plate layer, a cooling water merging layer, an auxiliary soldering tag layer and a bottom cover plate layer of the longitudinal cooler system are stacked up from the bottom up in sequence; the layers are tightly sealed through a welding manner; and a water incoming channel and a water outgoing channel between the layers form cooling loops with a water outlet and a water inlet of a temperature control refrigeration device. A heat dissipation channel formed through layer-by-layer subdivision of the water incoming channel enables the upper cover plate layer to be cooled into a heat dissipation surface, the temperature distribution of which is uniform, so that heat generated by the laser crystal attached on the heat dissipation surface in the working process can be taken away efficiently, uniformity of transverse temperature of the laser crystal is kept, thermal gradient and thermal stress in the laser crystal are reduced, and normal work of the laser is ensured.