Energy is an important basis in economic growth and consequently improvement of life quality. Energy integration of process plant is an example on management of energy consumption which has a considerable influence on our invirontment. Distillation unit of refineries is one of the most energy intensive.This work presents energy integration and retrofit of heat exchanger network with minimum capital invensment for existing distillation unit of Isfahan refinery. The Isfahan refinery capacity enhancement cause to high thermal load in the furnace atmosphere and create a bottleneck in operational process. The purpose of this project is to present the method for heat exchanger network improvement in order to save more energy and eliminate the network bottleneck of the refinery distillation unit, using pinch technology.beacuse of the topology trap existence at unit it is somehow impossible to use the current ways which are the base of investment level converters process the process, also in heat exchangers network refining ways the unit process restrictions is considered as a secondary restrictions. And should be use after revision that cause to network operation and real situation.In other hand, the ignorance of surveying pressure drop which is the result of higher level design, often cause to replacement or increase the network pumps and results to incorrect cost for goals.The other setback in use of current methods is the existence of intermediate products in the network.The purpose of solving these problems, in this project the new method base on the effect of increasing the cost of energy save the economy in the network is presented. That the network allowance drop is simultaneously surveyed with system operations limits and intermediate products at each phase simultaneously, therefor at the end of designing process it is not necessary to analyze the system dynamically and separately, and all units are fully integrated and simultaneously modify.In this project after presenting the new method for target and network refinery the essential data is simulated by Aspen HX-NET in order to simulate the network extraction and Isfahan refinery of distillation pre- heat network.Then the current situation is surveyed and solution for resolving the unit operation problem at first network refinery phase presented.In order to improve the network,8 membrane with total surface of 1839.9 square meter and 577829$ investing cost is added to this project and by increasing 23.4°C at the entrance of furnace , the furnace heat load 14975kj/s (equivalent to 19.5%) reduced and would save 1968149$ cost in total consumer saving. Key words : Heat Exchanger Network, New Retrofit Method, Simulation, Operations Limit, intermediate products, Pressure Drop