This research was on the acclimation and isolation of a bacteria strain ZXW01 with the ability to synthetize silver nanoparticles via reducing silver ion in its gradient of nitrate concentration. Based on morphologic observation, physiology and biochemistry tests and 16S rDNA analysis, the results proved that the bacteria was close related to Bacillus amyloliquefaciens with 99% similarity in its 16S rDNA sequence from the point of phylogenetics. Silver nanoparticles biosynthesized by the bacteria were spherical and equally distributed with the size between 2 nm to 18 nm from the analysis of X–ray diffraction, transmission electron microscopy (TEM) and thermogravimetric, and the productivity of silver nanoparticles was 80.6%.