In order to prepare a new type of safe, stable and efficient nano silver composite antibacterial agent, silver nanoparticles/chitosan (AgNPs/CS) was biosynthesized by by one-step method using Chimonanthus praeco
petal extract and chitosan as reducing agent and stabilizing agent, respectively. The optimal preparation procedure was determined by single factor experiment. The products were characterized by UV-vis absorption spectroscopy, transmission electron microscopy and X-ray diffraction, and their antibacterial activity, anti-drug resistance, stability as well as biological safety were comprehensively evaluated. The experimental results showed that the AgNPs/CS had the characteristic absorption peak of AgNPs at 451 nm, and the evenly dispersed AgNPs were spherical with average diameter of 12.83 nm, and the crystals had a face-centered cubic structure. The AgNPs/CS show antibacterial activity against aquatic pathogens both in vitro
and in vivo
, and had excellent anti-drug resistance, biosafety and stability. Therefore, AgNPs/CS is an ideal composite antibacterial agent, which has a prospective application in aquaculture field.