A process for preparing asparagine-linked oligosaccharide derivatives including the steps of: (a) treating a delipidated egg yolk with a protease to obtain a mixture of peptide-linked oligosaccharides, (b) treating the mixture of peptide-linked oligosaccharides with a peptidase to obtain a mixture of asparagine-linked oligosaccharides, (c) introducing a lipophilic protective group into the asparagine-linked oligosaccharides in the mixture to obtain a mixture of asparagine-linked oligosaccharide derivatives, and (d) subjecting the mixture of asparagine-linked oligosaccharide derivatives to chromatography to separate the mixture into individual asparagine-linked oligosaccharide derivatives.