Formation and properties of Ag sols fabricated in aqueous solutions of linear and branched polyelectrolyte matrices using ascorbic acid and hydrogen as reductant was studied at pH = 12. Alkaline medium was used to prove the difference of the AgNPs nucleus onto carboxylate and carbamide groups of polymer matrix. The structure of the host polymer affects the process of AgNPs formation in aqueous solution. It was proved the difference in the nucleation process for nanoparticles formation in carbamide and carboxylate groups. The aggregation of both types of AgNPs leads to forming of polydispersed polygonal nanoparticles in sols synthesized with both reductants.