Currently the metallic nanoparticles, in particular of noble metals like gold are gaining importance due to their potential applications in various fields, as their physicochemical properties and their low toxicity the materials become of great importance. In this paper the synthesis of gold nanoparticles was carried out in solution using a reducing agent as is the biomolecule chitosan as reducing agent and were also characterized by a spectrophotometric technique as ultraviolet visible to verify the efficiency of the synthesis process, the spectrum showed that the synthesized nanoparticles have an absorption band at 525 nm. characteristic of gold particles to nanometric size.