Abstract: In order to analyze the core factor of cooling effect of jet array impingement unit of disk-laser crystal module, the effect of apertures, hole-to-hole spacing and nozzle-to-plate spacing on jet array impingement cooling was analyzed by numerical calculation under certain total area of each nozzle. Heat transfer coefficient was analyzed comparatively by experiment. The cooling effect was verified in actual disk laser. The results show that nozzle B of hole aperture 0.6mm and hole-to-hole spacing 1.6mm has the highest heat transfer coefficient. Heat transfer coefficient can reach 55000 Wm-2K-1 at water flow rate of 3 L/min and nozzle-to-plate spacing of 3mm. There is optimum value of nozzle-to-plate spacing at different inlet pressures. The optimum value of nozzle-to-plate spacing of nozzle B is 0.5mm at inlet pressure of 0.2 MPa. Verification experiment on actual disk-laser shows that the cooling temperature of nozzle B declines 5℃ lower than of nozzle C, at water flow rate of 6.5 L/min, nozzle-to-plate spacing of 5mm and current of 200A. The conclusion provides a reference for the design and the optimization of jet impingement cooling unit of thin-disk laser crystal module.