Abstract: Nano-sized barium titanate (BaTiO<SUB>3</SUB>) powder was synthesized by one-step method under atmosphere pressure with inexpensive TiCl<SUB>4</SUB>,BaCl<SUB>2</SUB>,and NaOH as raw materials.Effects of various factors,such as hydrolysis degree of TiCl<SUB>4</SUB>,pH,reaction temperature,and surfactant on the purity and morphology of the prepared nano-sized barium titanate powder,were researched.Results indicated that,under the best of technological conditions,nano-sized BaTiO<SUB>3</SUB> powder was uniform and spherical in shape and belonged to cubic syngony with size distribution of about 20 nm,purity of 99.85%,and amount-of-substance ratio of Ba／Ti of (1.000±0.005).Comparing with hydrothermal synthesis method,this one have the advantages of lower temperature,lower pressure and roasting-free etc..