Background and purpose: The wastewater discharged from textile industries is one of the main environmental pollutants that causes many problems for the environment if it is not treated or discharged. The present study compared Fenton oxidation process with coagulation and flocculation using the natural coagulant of Sodium Alginate in order to remove Reactive Red 198 Dye. Materials and methods: This study was carried out in an experimental scale, in which the effects of pH, concentration of the dyeing substance, concentration of iron sulfate and hydrogen peroxide for the oxidation of Fenton and the effects of pH, concentration of coagulant, concentration of dyeing substance, and the Coagulant Aid of Sodium Alginate were all investigated. Results:The results of the current study indicated that in the Fenton process, the efficiency of RR 198 Dye removal under acidic conditions (pH=3) at optimal conditions was achieved to be 96.2% for the dye with the concentration of 20 mg/l. By using 70 mg/l of the coagulant of Poly-Aluminum Chloride in coagulation and flocculation process, 71.2% of the dye removal was obtained for the initial concentration of the dye as 20 mg/l. Also, by adding 50 mg/l of Sodium Alginate to the optimal concentration of Poly-Aluminum Chloride, the dye removal increased up to 92.1%. Conclusion: Although under optimal conditions, the efficiency of coagulation process with coagulant aid was only 4% less than the efficiency of Fenton process, considering the advantages of Fenton oxidation including lack of production of excessive sludge, a higher efficiency was gained at large doses of dye.