Population growth, improve of living standards, and development of industry and agriculture are among the factors that cause an increase in water consumption and wastewater production leading to environmental pollution. Generation of large amounts of industrial wastewater in the oil and gas industry is one of the major environmental problems in the oil-rich regions. Industrial wastewater treatment using coagulants with high efficiency can reduce the effects of environmental pollution due to the reuse and discharge of wastewater. In this research, the effect of ferric chloride and aluminum sulfate coagulants (alum) in the wastewater treatment of desalination plants of Gachsaran oil and gas exploitation company using Jar test method was studied. Performance of used coagulants in the various concentrations (5, 10, 15, 20 and 30 mg/L) to reduce the amount of total suspended solids (TSS), biological oxygen demand (BOD 5 ), chemical oxygen demand (COD), oil and turbidity was determined and compared. The highest percentage reduction in the TSS, oil, turbidity, BOD 5 and COD for ferric chloride was obtained at concentrations of 15, 15, 10, 20 and 30 mg /L, respectively. Also, the most reduction in the parameters of TSS, oil, turbidity, BOD 5 and COD for aluminum sulfate was at concentrations of 20, 30, 30, 20 and 30 mg/L, respectively. The most effect of ferric chloride coagulant was observed for turbidity, TSS and oil and the least effect for COD and BOD 5 parameters, respectively. The most effect of aluminum sulfate was for oil, turbidity and TSS and the least effect for the parameters of COD and BOD 5 , respectively. Overall, the results showed that the ferric chloride coagulant had more efficiency than alum for reduction of studied parameters in the wastewater treatment. Keywords: Coagulants, Ferric chloride, Aluminum sulfate, Desalination wastewater