Two kinds of relatively steady colloids containing silver nanoparticles were prepared by Sol-Gel method using sodium tetrahydroborate as reducing agent.The samples were characterized by optical absorption spectra and transmission electron microscopy.UV-Visible absorption spectra show that the size of silver nanopaticles is small when the concentration of Ag+ was low and the absorption band was belonged to dipole resonance of nanoparticles.The size of nanoparticles became larger with the increase of the concentration of Ag+.The dipole and quadrupole oscillation contributed to the optical absorption spectra.It was also found that the shapes of the absorption bands kept their shapes when the colloids containing silver nanoparticles were diluted.However

the peaks of absorption were red-shifted with the biggest shift of 10 nm.TEM study showed that the size of Ag nanoparticles in low concentration colloid was uniform with average size of 12 nm.The Ag nanoparticles in high concentration colloid had a dual-mode size distvibution with little nanoparticles smaller than 14 nm and others larger than 20 nm.