In order to probe the nature of regeneraion on the sulfated Cu/SAPO-34 selective catalytic reduction catalysts, CHA structure, copper species, and NO, conversion were investigated. A sulfated Cu/SAPO-34 catalyst was treated at different temperatures and times. The ammonia-sulfate species was removed at 500 degrees C, and copper sulfate was completely decompose at 750 degrees C. The NO, conversion of sulfated catalyst gradually recovers with the degree of regeneration increasing. XRD and ex situ DRIFTs results show that thermal treatment presents no effect on the framework structure of Cu/SAPO-34. The TPR and EPR results suggest that thermal treatment has an influence on the number of isolated Cu2+ and CuO instead of coordination environment and redox ability. However, the apparent activation energy of fresh, sulfated, and regenerated catalysts for SCR reaction remains the same, and turnover frequencies are also identical. The study reveals that the activity recovery is attributed to the increased number of active sites by sulfate species decomposition and migration effect.