In order to effectively control the resistance rise of horizontal tube primary cooler and stabilize the process index of primary cooler, the reasons of naphthalene formation in primary cooler were analyzed, such as the disadvantages of upper section spraying of circulating ammonia water or condensate, the nozzle holes of spraying pipe were easily blocked, resulting in uneven spraying and reduced spraying density, unstable spraying liquid quality, affecting the effect of absorbing naphthalene, etc on this basis, the lower liquid return main pipe after naphthalene spraying and washing was reformed, and the new pipe was added to the new vent tank, so as to achieve the purpose of separate hot washing primary cooler, and optimize the key steps of daily operation. Practice has proved that through the above transformation, the operation effect of the initial cooler section is good at present, after two months of operation, the resistance of the initial cooler has not been found to rise, and it remains within 1 500 Pa.It can realize continuous and stable operation.