Abstract: To explore the effect of saturated fatty acid carbon chain length on the structure and in vitro digestive properties of waxy wheat A and B starch-lipid complexes. Using waxy wheat A and B starch as the main raw materials, after being modified by compound enzymes, they were compounded with lauric acid, myristic acid, palmitic acid and stearic acid respectively, and the compound index (CI value), the solubility and swelling power, iodine absorption characteristics, crystal structure, fourier transform infrared spectroscopy and predicted glycemic index (pGI value) were investigated. The results showed that with the increasing of carbon chain (12~18), the CI values of starch-lipid complexes of waxy wheat A and B decreased from 53.66% to 38.15%, and from 60.35% to 41.04%. The solubility and swelling power of starch-lipid complexes of waxy wheat A and B increased gradually with the increasing of temperature and the number of carbon atoms. The solubility and swelling power of waxy wheat A starch-lauric acid at 90 ℃ were 1.99% and 3.34 g/g, the solubility and swelling power of waxy wheat B starch-lauric acid at 90 ℃ were 1.74% and 3.18 g/g respectively. Among the four lipid complexes, the complexes formed by waxy wheat starch A, B and lauric acid had relatively high crystallinity, reaching 25.37% and 23.50%, and their ratios at 1047/1022 cm⁻¹ were also high, which were 0.993 and 0.989. Compared with the uncomplexed lipid-modified waxy wheat starch, the pGI values decreased significantly, from 47.63 to 36.61, and from 48.30 to 35.49 respectively. This study can provide a reference for the structure and in vitro digestion characteristics of starch-lipid complexes.