Abstract: This study was aimed to assess the effects of different sources of selenium on the morphological characteristies ofpapillae in the atrium ruminL of Tan sheep lambs. A total of fifty healthy male Tan sheep lambs with similar body weight and age（about 45-day-old） were randomly and averagely assigned into two groups： the control group fed a diet supplemented withsodium selenite, the experimental group were fed with the diet supplemented with selenium yeast. The content of selenium in bothof the two diets was 0.30 mg/kg DM. The lambs were slaughtered and their tureen samples were recovered after a sixty-dayfeeding trail. The height, width and density of the papillae in the atrium ruminis of the lambs were determined with verniercaliper. The results showed that the lambs in experimental group had significantly higher height, width and density of the papillaein the atrium rttminis compared to the control group （P〈0.05） ; slightly higher thickness of stratum eorneum and width of laminapropria were observed in the arium ruminis of the lambs in experimental group compared to the control group （P〉0.05）. It wasindicated that the dietary supplementatinn of 0.30 mg/kg of selenium yeast performed better in promoting the growth anddevelopment of papillae in the atrium ruminis than supplementation of sodium selenite.