Extraction and processing of oil products consume 10% of the total energy produced by fossil resource. to prevent operational problems in downstream units Oil extracted from oil fields will be sent to the desalting plant for desalination and dehydration. One of the most important steps that have a vital role in this unit is pre-heating by heaters which use natural gas produced with crude oil at the same time.   Iran is known as the area with the potential for utilization of solar systems. Investigations on  Solar thermal technologies showed that Linear Fresnel concentrator has high performance as a  solar auxiliary system for conventional heaters And leads to an annual reduction of 1.5 million cubic meters of natural gas consumption in a desalination plant. The Gas is saved can be used for feed of petrochemical plants. Investigation on the cost-benefit payback time of proposed system shows that solar Fresnel designed according to the conditions and potential of solar radiation at the site of the study is a little more than a year. Such an investment is economically justified and reduces fuel consumption and reduce carbon dioxide emissions resulting from the combustion gas. A 27% share of solar power in the supply of the thermal energy required for crude oil desalination is a step towards achieving the goals of sustainable development in the upstream oil industries.