Abstract: Corrosion of trays at the top part of fractionator in delayed coking unit of SINOPEC Luoyang Petrochemical Company was detected during revamping, thus, an analysis of corrosion causes was carried out. It seemed that using high salt feed and recycling heavy waste oil with high salt and high water content were the main causes, as well as improper operation of washing step. Considering the feed properties, operation parameters and equipment conditions, some countermeasures were applied, such as strengthening the monitoring of salt content in feed, improving the heat distribution at the top part of fractionator, adding a water pipe for washing at the top part of fractionator, optimizing the side streams recycle and so on. Since then, the salt deposition in fractionator was improved significantly, and it is good for a long-term operation.