The invention provides a comprehensive utilization apparatus for the heat energy of a tail gas absorbing tower. The upper part of the tail gas absorbing tower is connected with a demineralized water cooler through a pipeline; the lower part of the tail gas absorbing tower is connected with a tail gas cooler through a pipeline; the bottom of the tail gas absorbing tower is connected with a tail gas absorption liquid tank through a pipeline; the demineralized water cooler is connected with the tail gas cooler through a liquid ammonia pipeline; the bottom of the tail gas cooler is connected with the feed inlet of an ammonia evaporator through a pipeline; and the ammonia evaporator and the tail gas absorption liquid tank are separately connected with an ammonia oximation reaction vessel through pipelines. The comprehensive utilization apparatus is simple in flow and low in equipment investment cost. According to the invention, heat released in the process of ammonia gas absorption by demineralized water can be used for evaporation of liquid ammonia, so the amount of steam needed in gasification of liquid ammonia is reduced and the solubility of tail gas in the demineralized water is increased by decreasing the temperature of absorption liquid; and thus, the addition amount of the demineralized water added into the tail gas absorbing tower is decreased, and the purposes of energy conservation and consumption reduction are eventually achieved.