Abstract: Taking a delayed coking unit (DCU) in a domestic refinery as the research object, the feed preheating process was simulated by PRO/Ⅱ，the process simulation software. Considering the trait of the heat exchange network for DCU, the strategy of pinch analysis was introduced to calculate the highest theoretical heat exchange temperature for the feed, taken as the target temperature for the retrofit of the feed preheating process. In a case study, the quantitative energy grade and heat duty (ε-Q) diagram was constructed. By calculating the exergy destructions, it is found that the “bottleneck” of the preheating process is exergy destructions from mixing and heat exchange processes with large temperature differences. According to the principle of “counterpart temperature, cascade using”, the feed preheating process was retrofitted. The case study results show that the exergy destruction of mixing process is decreased by 80% and the exergy destruction of heat exchange process for preheating the feeds per 1℃ increase is decreased by 24.1% after the retrofit. Meanwhile, the final heat exchange temperature of feed is increased by 43℃. The heat duty of the coking furnace is decreased by 4.2MW, which indicates that the effect for energy saving is obvious.