Analysis was conducted on the optimization of heat exchanger networks of propylene oxide production system using chlorohydrin method based on pinch technology, and the optimization methods of whole system and subsystems were used to compare with each other for better optimization method. Aspen software was used to verify the data of each stream taken from the whole process system and to calculate and analyze. The results showed that the current network temperature difference of pinch point was 30 K, the temperature of pinch point of the whole system was 329.5 K and the temperature of pinch point of subsystems was 327, 329.5 and 317.2 K, respectively. The optimization method of whole system heat exchange network could achieve energy saving target for 595.3 kW which took up 17.47% and 5.23% of the hot and cold utilities of original system. The optimization method of subsystem heat exchange network could save 610.6 kW which took up 17.91% and 5.36% of the hot and cold utilities of original system. The optimization method of subsystem heat exchange network was better for the optimization of heat exchanger network of propylene oxide production system using chlorohydrin method.