Abstract: The molecule self-assembly technology was used to prepare astaxanthin/whey protein nanocomplex, and the interaction mechanism between astaxanthin (AST) and whey protein was studied. By controlling the proportion of astaxanthin organic solution and whey protein aqueous phase, whey protein (α-lactalbumin, β-lactoglobulin, whey protein concentrate and bovine serum albumin) and astaxanthin were used for preparing well formed H aggregates or J aggregates astaxanthin/bovine serum albumin nanocomplexes, the resultant H/J AWC-NPs were spherical with 150~430 nm diameter, polydispersity index (PDI) showed good dispersity and −12~−1 mV Zeta potential measured by dynamic light scattering (DLS). Both H aggregates and J aggregates astaxanthin/whey protein nanocomplexes were near spherical with clear and smooth edges by transmission electron microscopy (TEM). The analysis by ultraviolet-visible absorption spectra revealed that the absorption maximum λ_max of astaxanthin H aggregates was shifted from 480 nm of astaxanthin monomer blue to 388 nm, and the absorption maximum λ_max of astaxanthin J aggregates was shifted red, showing a parallel peak at about 519 and 556 nm. The fluorescence spectrum analysis showed that the fluorescence intensity of astaxanthin/whey protein nanocomplex was significantly enhanced due to the specific structure of astaxanthin aggregates, and hydrophobic amino acids and hydrophobic regions in whey protein were exposed. In this study, the water dispersion of astaxanthin and its aggregates and the characteristics of whey protein carrier were investigated to provide theoretical basis for its subsequent development and application in the field of food and medicine.