This study shows a water cooling system by using a steam ejector and jet condenser to drop the temperature of the water by about $5^{circ}C;from;25^{circ}C$ or higher. In this research, to replace the present water cooling system, we focused on a water cooling system by latent heat of evaporation, thus this system needs a vacuum pressure to evaporate the water in enclosed tank. The water cooling effects are depended on the vacuum pressure in the enclosed tank, and the cooling water is generated by latent head of evaporation. As the experimental results, the absolute vacuum pressure obtained was about $5{sim}8$ mmHg using a steam driven ejector with jet condenser.