Selenium (Se)-rich soil is the precondition of selenium-rich industry. Based on the 1︰50 000 geochemical survey of soil environmental quality and long-term positioning observation, the proportion of Se-rich soil and the causes and influential factors of Se-rich soils in Xunyu plain were studied. The results showed that soil Se contents in Qintang, Guiping, Pingnan and Gangnan were higher than national average (0.29 mg/kg). Se content in Qintang was the highest (0.77 mg/kg). The proportion of the soils with Se content more than 0.4 mg/kg in Qintang, Guiping and Pingnan all exceeded 50%, highest in Qingtang (88.5%). Topsoil Se in Guiping was mainly inherited from parent material. Soil Se content was negatively related to pH. Se contents reached 0.58 mg/kg in soils with pH<5. Soil Se content was in an order of forest land > grassland > garden plot > paddy field. Soil Se content in paddy field was 65.45% of the forest land. These results indicate that the soils in the Xunyu plain are rich in Se, soil parent material, land use type and soil pH are important influential factors on soil Se content.