Abstract: The allergic epitopes of α-lactalbumin are the molecular basis for allergenicity. In this paper, the effects of different lengths sugar chains on the structure and allergenicity of allergic epitopes in α-lactalbumin were investigated. The IgE linear epitopes of ¹³KDLKGYGGVSLPEW²⁶ (¹³K-W²⁶) were synthesized and glycated with glucose, maltose, maltotriose and maltopentaose. Then the structural changes were analyzed by spectroscopy and chromatography. Cellular assays and ELISA were used to evaluate the histamine, interleukin-4 and interleukin-6 release ability of KU812 cells and the IgE binding ability. The results showed that ¹³K-W²⁶ was glycated by different lengths sugar chains significantly decreased the free amino content and changed the fluorescence intensity and UV absorption intensity, and decreased the IgE binding ability and the release ability of histamine, interleukin-4 and interleukin-6 in KU812 cells. Therefore, different lengths of sugar chains can change the structure of ¹³K-W²⁶, and reduce the allergenicity. The order was maltopentaose>maltotriose>maltose>glucose. In conclusion, the sugar chains could mask the linear epitopes ¹³K-W²⁶ of α-lactalbumin, the sugar chains with longer length had stronger masking effects on epitopes, the better the effect of reducing the allergenicity.