Using sodium hypophosphite as the reducing agent, polyvinyl pyrrolidone as the protecting agent, the nanosized silver powder was synthesized by chemical reduction method in a highly concentrated silver nitrate solution. Using the orthogonal design method of three factors and three levels, the optimal conditions to prepare the nanosized silver powder were obtained by studying the effects of following factors, such as the concentration of reducing agent, the doses of protecting agent and the temperature, on the particles size and morphology of silver powder. The pure nanosized silver powders with qusai-spherical shapes and homogeneous distribution and diameter of 30 nm to 50 nm were synthesized under the conditions of AgNO3 concentration of 1.0 mol/L, NaH2PO2·H2O concentration of 0.1 mol/L, PVP/AgNO3 weight ratio of 1∶1, pH=1~2 and at 40 ℃