Colloidal silver nanoparticles were synthesized respectively in three water-in-oil microemulsions, i.e., the microemulsion composed of SDS, cyclohexane, isoamylalcohol and water, the microemulsion composed of AOT, cyclohexane and water as well as the microemulsion composed of AOT, dodecane and water. The UV-Vis absorption spectroscopy was used for confirming the formation of silver nanoparticles, and the TEM was also used for elucidating the structure of resultant particles. The UV-Vis spectra show that the maxima of absorption peaks are at 400 nm, 428 nm and 435 nm, respectively. The UV-Vis spectrum is narrow with a high absorption density in SDS microemulsion. However, the silver particles formed in AOT-dodecane-water microemulsion have the broadest plasmon peak and the lowest absorption density. The TEM images confirm that the nanoparticles are all spherical with mean diameters of 6.46 nm, 4.03 nm, and 1.78 nm, respectively. There are not agglomerated particles in the three microemulsions. The growth mechanism of spherical silver particles is thought to be that the spherical reverse micelles in microemulsions offer a special microscopic template for the formation of silver namoparticles, and thus there is a relation between the droplet size and the radii of the formed particles. However, the size and morphology of the particles do not directly follow the shape and size of the microemulsion droplets due to the collision and coalescence. That is to say, the final silver nanoparticles are not perfectly monodisperse and have a breadth in size distribution