The invention relates to a preparation method of a single component of high-purity oligomate, comprising the following steps of: separating crude oligomate by using 005*7 cation exchange resin to remove glucose effectively and obtain the oligomate product containing less amount of lactose with the purity above 85%; taking the oligomate product as a raw material, separating once by using a polyacrylamide gel column to obtain the single component of oligomate with the purity higher than 85%. The single component is separated for the second time through the polyacrylamide gel column to obtain the standard product of the single component of with the purity higher than 85%.