Abstract: In recent years,production and processing of natural selenium-rich agricultural products become a research hotspot. The main factor affecting the selenium content in soil was effective form . So it was particularly important to understanding the conversion relationship of selenium forms in the soil and find ways to improve selenium effectiveness. By analyzing the past research on selenium in soils, this paper analyzes the classification of soil selenium morphology, the transformation of soil selenium morphology and the factors that improved the validity of selenium. Insight into the relationship between chemical form and leaching form of selenium in soil,study the conversion factors of different forms of selenium. Looking for ways to improve selenium effectiveness in rich selenium areas. Combining soil and crop characteristics of different rich selenium regions,taking different selenium activation methods, provide more scientific evidence for the research.