The present invention relates to a method for preparing a lactose-containing powder. Said method includes the consecutive steps of: a) concentrating a lactose-containing liquid so as to obtain a concentrated liquid having 55% to 65% dry matter content, said concentration Step a) having a duration between 10 and 20 minutes； b) overconcentrating the concentrate obtained from Step a) so as to obtain an overconcentrated material having 75% to 80% dry matter content, said overconcentration Step b) having a duration varying from 2 to 10 minutes； c) granulating the overconcentrate obtained from Step b) by mixing said overconcentrate with a lactose-containing powder, having at least 95% dry matter content, until a granulated powder having dry matter content with at least 85% dry extract is obtained； and d) drying the granulated powder obtained from Step c) so as to obtain a lactose-containing powder having at least 95% dry matter content.
