Abstract: Heat exchanger network (HEN) is an important subsystem for energy recovery in process units. The energy utilization efficiency can be effectively improved by optimizing HEN. In order to guide the retrofit of HEN, it is necessary to analyze HEN, point out the energy saving potential and evaluate the difficulty of the energy saving. Based on Pinch technology, the relationship between the actual heat utility consumption and the minimum heat utility requirement is analyzed, and the difference value of them is regarded as the energy saving potential of HEN in this paper. On this basis, an energy saving potential index for evaluating the difficulty of the energy saving is presented, which is the ratio of the energy saving potential to the heat of hot streams in the Pinch section. In addition, the proposed index is applied to the heat integration between different process units. A case study of HEN of a delayed coking unit and a fuel hydrotreating unit is carried out, and the result shows that the energy recovery is increased by 4 537 kW.