Abstract: L-cysteine can significantly reduce the content of acrylamide and form new substances. To clarify the reduction mechanism and apply it in potato chip processing, a high purity cysteine-acrylamide adduct was prepared. The target adduct was synthesized by optimizing the reaction conditions, followed by reversed-phase column chromatography for separation and purification. Its structure was identified by mass spectrometry, nuclear magnetic resonance and ultraviolet spectroscopy, and the reduction mechanism was correspondingly elucidated. The cytotoxicity of adducts was evaluated with Caco-2 cell line. Furthermore, potato chips were pretreated with cysteine solutions and the reduction of acrylamide was detected by UPLC-MS. The results showed that the adduct with 95% purity could be obtained when the optimum reaction ratio of cysteine and acrylamide was 1:3 at 120 ℃ for 3 h. Its molecular formula was C₆H₉NO₃S, with relative molecular weight of 192.0641 and maximum UV absorption wavelength of 196 nm. It was formed by Michael addition reaction between the sulfhydryl group of cysteine and the alkenyl group of acrylamide. Compared to acrylamide, the cytotoxicity of the adduct was significantly lower after 24 and 48 h treatment. Potato chips soaked in cysteine solutions of 3 and 5 g/L before frying obtained over 83% of acrylamide reduction rate. In addition, a certain amount of adduct was detected in such potato chips, indicating that cysteine could significantly reduce the acrylamide content in fried potato chips by forming acrylamide adduct.