The thermal and chemical stabilities of the colloid silver nanoparticles prepared by bioreduction were investigated in virtue of UV-Vis spectrometer. The results indicate that UV-Vis spectra of silver colloid prepared by bioreduction have not significant change after heat treatment at 100 oC for 6 h. Hydrogen ion and the electrolyte with multivalent cation markedly influence stabilities of the silver colloid, while hydroxide anion has a weak influence on its stability. Thermal and chemical stabilities of the silver colloid prepared by bioreduction are superior to that of the silver colloid prepared by the sodium citrate reduction method