The causes of blockage of the benzene hydrogenation heat exchanger are introduced,and the raw materials,demineralized water,parameters and washing wastewater are analyzed.Measures are taken,such as on the one hand,the quality control of feedstock is strengthened,and on the other hand,the water injection point and its amount are adjusted in time,so that the ammonium salt in the shell side of the pre-evaporator can be eliminated.