Abstract: A new electrolytical reduction for determining silver silver size and distribution was studied. The corresponding instrument developed was computerized with a PC computer.All operaations including acquistion,recognition and digital conversion of signals as well as data processing were performed automatically.With thes instrument a variety of AgX with diameters between 0.1-40μm could be measured accurately.By comparison with other usually used methods,such as the graphiccal -statistical analysis by EM,the centrifugal method and laser scattering method, this new method was more rapid and accurate in measurements.Besides,the developed instrument had its features in low cost and ease to master and operate.the results obtained from both eletrolytic reduction and EM were also compared in this article.