Abstract: With sodium dodecyl sulfate as soft template,selenium nanoparticles was prepared by using&nbsp; ascorbic acid to reduce selenious acid （H<SUB>2</SUB>SeO<SUB>3</SUB>）.Prepared nanoparticles were characterized,influences of reaction conditions on morphology and particle size of the product were studied.Results showed that when the concentration of H<SUB>2</SUB>SeO<SUB>3</SUB> and ascorbic acid in the reaction system are 0.01 mol/L and 0.07 mol/L respectively,concentration of sodium dodecyl sulfate is 1.0% （mass fraction）,and reaction time is 7 min at room temperature,the uniform,stable red spheric selenium nanoparticles with average size of about 35 nm can be obtained.Prepared nanoparticles can be stably stored for more than two months after treatment of ultrasonic wave.