The invention discloses a coal gasifier ash cooler. The coal gasifier ash cooler comprises a cylinder. An upper seal head and a lower seal head are welded to the two ends of the cylinder. A pluralityof sets of vertical S-shaped pipe bundles are arranged in an inner cavity of the cylinder and distributed in a radiation manner in the radial direction with the center axis of the cylinder as the center. Water inlets of the S-shaped pipe bundles communicate with a cooling water inlet box surrounding the outer portion of the lower seal head, and water outlets of the S-shaped pipe bundles communicate with a cooling water outlet box surrounding the outer portion of the upper seal head. A rigidity ring lug type support is arranged on the outer wall of the cylinder. The cooler is of a vertical structure, and the occupied area is small. Through the S-shaped pipe bundles in the cylinder, the heat exchange area between the pipe bundles and ash is effectively increased, and the heat exchange efficiency is improved. The cooler is of a welding structure, the connecting part between the cooler and a coal gasifier is of a welding structure as well, flange sealing is avoided, the coal gasifier ash cooler is suitable for pressured work conditions, and the sealing performance is good. In the using process, ash settlement depends on gravity of ash, motor transmission is not needed, and energy consumption is reduced.