The present invention discloses a polymeric polyamine which can be produced by polymerizing polyoxyalkylene-amine and a linker. The linker can be anhydride, carboxylic acid, epoxy, isocyanate or poly(styrene-co-maleic anhydride) copolymers (SMA). The present invention also discloses a method for stabilizing the Ag nanoparticles with polymeric polyamine. The polymeric polyamine serving as a stabilizer or dispersant is mixed with a water solution of silver salt and then a reducer is provided to reduce the silver ions and form an organic or a water solution of Ag nanoparticles. Water or solvent of this solution can be further removed through a heating, freezing or decompression process, and thus solid content of the solution can be increased. The concentrated solution also can be diluted to obtain a stable dispersion without aggregation.