The invention discloses a cold supply system combining an indirect-evaporation cooling tower with mechanical refrigeration for a data center. The cold supply system comprises a composite type refrigeration system which is connected with a heat exchange device, wherein the heat exchange device is arranged on the upper part of an equipment cabinet sealing thermal channel in a data center. The cold supply system disclosed by the invention sufficiently utilizes an outdoor natural cold source, and realizes green, energy-saving and environment-friendly requirements of a data room.