The invention relates to a monitoring system of an intermediate cooling system of an aluminum oxide decomposing tank. The monitoring system comprises a PH sensing module, a temperature sensing module,a control module, a display module and a storage module, wherein the PH sensing module is used for collecting PH value data of circulating water from a circulating water inlet and a circulating wateroutlet of a heat exchanger and transmitting the data to the control module; the temperature sensing module is used for collecting temperature data of the circulating water from the circulating waterinlet and the circulating water outlet of the heat exchanger and transmitting the data to the control module; the control module receives the data transmitted by the PH sensing module and the temperature sensing module, carrying out operation comparison on the received data to obtain an analysis result, and outputting a working instruction to the display module according to the analysis result; the display module displays the analysis result of the controller; the storage module is used for storing an operation result of the control module and the received data. Real-time monitoring for the intermediate cooling system is realized; seepage of decomposing liquid and blockage of the heat exchanger can be found in time to avoid accident expansion.