Abstract: A systematic study on the geochemical characteristics and influencing factors of selenium (Se) in soil and crops of Horqin district, Tongliao City, shows that the Se content in the soil is generally low with uneven spatial distribution and only partially reaching the Se-sufficient level. Se is mainly concentrated in surface soil and positively correlated with organic carbon, Al₂O₃, TFe₂O₃, Mn and P, showing that the organic carbon, clay minerals and Fe-Mn oxides significantly affect the geochemical behavior of Se. The soil in the study area is alkaline to strongly alkaline. However the Se-rich crops are not strictly produced in Se-rich soil. Therefore, the development of Se-rich agricultural products should comprehensively consider such factors as Se content, available Se content in soil, Se content in crops, soil physicochemical property and geographical landscape.