The corrosion damage mechanism of heat exchanger in visbreaking unit was studied, through field morphology observation, scanning electron microscopy (SEM) micromorphology, energy spectrum analysis (EDS) and corrosion coupon experiments, and find out the naphthenic acid corrosion damage reason of the exchange tube heat exchanger and baffle plate, further analyzes the naphthenic acid corrosion mechanism of carbon steel; Then through a variety of material corrosion coupon experimental comparison, the anti⁃corrosion measures are put forward. The research results show that the corrosion of heat exchanger leakage and crude oil viscosity device, high acid value, the water content of the working temperature of heat exchanger and the material, dehydration of crude oil and reasonable change of the working temperature and material of the heat exchanger can effectively reduce the corrosion damage of the heat exchanger of the viscosity reducing device.