Epigallocatechin gallate (EGCG) primarily extracted from green tea, exhibits significant antioxidant, hypolipidemic, and anticancer properties. Nevertheless, the limited aqueous solubility and bioavailability of EGCG impede its practical applications. Glycosylation modification of EGCG is an effective method for enhancing its properties. In the present study, a thermally stable variant of sucrose phosphorylase from Streptococcus mutans (SmSP) was identified as having catalytic activity for glycosylation of EGCG. The optimal temperature and pH for SmSP were determined to be 45°C and 6, respectively. The mono-glycosylation product of EGCG was structurally characterized as (-)-epigallocatechin gallate 4'-O-α-D-glucopyranoside. Under optimal reaction conditions (8 % methanol, 10 g/L EGCG, 300 g/L sucrose, 40 U/mL crude enzyme, 35°C, and 24 h), the conversion rate of EGCG reached 80.79 %. Hydrogen bonding interactions between the enzyme and ligands may enhance the stability and catalytic activity of SmSP. Two active site loops significantly influence the selective formation of EGCG glycosides. These insights expand our understanding of the structural basis of sucrose phosphorylases in the synthesis of EGCG glycosides.