Background and Aim: Dyes are one of the most important pollutants in textile wastewater (TWW). Use of advanced oxidation processes (AOPs) as an efficient method can be useful for removal of these pollutants from the effluent of textile wastewater. In this study we evaluated the efficiency of the persulfate activation process, using ultraviolet (UV), in the presence of granular activated carbon (GAC) for removal of methylene blue dye (MBD). Also, we studied the effect of operating parameters on the dye removal. Materials and Methods: This experimental study was performed in a pilot-scale batch photoreactor. The effect of operating parameters including solution pH (between 3 and 9), dosage of granular activated carbon (0.6-5 mg/L), persulfate concentration (0.2-2 mmol/L), initial concentration of methylene blue dye (50-400 mg/L), and contact time (2-30 minutes) were evaluated. The final concentration of methylene blue dye was measured by using DR-6000 device. Mineralization of the process, in optimal conditions, was determined by measuring COD and TOC. Results: The highest efficiency of the process for removal of methylene blue dye (99% dye removal at an initial concentration of 50mg/L) was observed at pH = 3, granular activated carbon dose of 1 g/L, optimal persulfate concentration of 1 mmol/L, and after a 20-minute contact time. The removal rates of COD and TOC were 71% and 69.9%, respectively, and the decomposition rate of methylene blue dye was based on the first-order reaction (R 2 = 0.99). Conclusion:Considering the results of this study, the combined process had a significant efficiency to remove methylene blue dye and can be used as an efficient method for removal of the dye from the effluent of textile wastewater.