Abstract: The effects of selenium on growth and differentiation of primary cultured neuron from thirteenth rat embryo midbrain were investigated.The cultures of cells were exposed to 0 01～10 0μmol/L Na₂SeO₃ and observed the changes of proliferation of neurons using MTT stain. The degree of differentiation and morphological changes of neurons were examined by means of scanning electron microscope and phase-contrast microscope.The results showed that low Se concentration (0.01～0.1μmol/L) can stimulate proliferation and differentiation of cultured neurons with a relationship of does-effect response.While the higher Se concentration (over 1.0μmol/L) can inhibit it, highest Se concentration(10μmol/L) can cause cytotoxicity.Low Se concentratation is helpful to growth and differentiation of neurons from rat embryo.