Abstract: The invention relates to a method for preparing a powdered polymer selected from a polyamide, a copolyamide or a copolyesteramide by anionic polymerization in a solvent solution, characterized in that the polymerization of the monomers) generating said polymer is made in the presence of a catalyst, an activator, at least one amide one of which is always a N,N?-alkylene bisamide, and an organic or inorganic filler, the amount of N,N?-alkylene bisamide added in the medium being determined based on the specific surface are desired for the powder particles, said powder particles having an essentially constant diameter or one depending on the desired mean diameter of the powder particles, said powder particles having an essentially constant specific surface area.