Abstract: Effects of tea polyphenols (TP) on the quality of the steamed bun was studied, and its molecular action mechanism was preliminary analyzed. The effects of TP on the specific volume, texture, hardening rate and α-starch content of steamed bun were systematically observed. And the effects of TP on the iodine binding capacity, solubility, swelling power and thermal properties of starch were determined. And then the molecular dynamics (MD) was used to study the interaction between TP and starch molecules. The results showed that TP had a significant effect on the specific volume and texture. Besides, TP could decrease the hardening rate (from 195 to 138 g/h) and increased the α-starch content of the steamed bun; the addition of TP decreased the iodine binding capacity, increased the solubility (from 8.3% to 38.1%) and swelling power (from 11.4% to 13.8%), and decreased the gelatinization peak temperature (from 62.21 to 53.57 ℃) for promoting the gelatinization of starch and delaying the retrogradation of starch. Furthermore, TP could interact with starch by hydrogen bonds (highest occupancy hydrogen bonds 4GA_12@O2: EGCG_1@H18, ratio was 5.6%), and changed the spatial configuration of starch molecules, leading to the variation of the physicochemical properties of starch. The results indicated that TP could change the physicochemical and quality characteristics of starch, and had potential value as a new starch modifier.