Silver halide nanoparticles have heen synthesized by the method of mixing two different Water-in-oil type, on containg silver ions and the other containing halide ions. Phase behavior experiments for ternery systems containg water, AOT surfactants and hydrocarbon showed that the chain length of a hydrocarbon caused a remarkable difference in phase region of a one phase water-in-oil type microemulsion, especially water contents contained in a microemulsion phase. photomicrographs obtained by transmission electron microscopy indicated that average particle size, particle size, distribution and number of particles forms are dependent on the initial composition of one phase water-in-oil type microemulsion, which obviously affected both intermicella exchange rate and rigidity of the surfactant shell.