Abstract: Based on the comprehensive collection of samples from the alkaline soil in the Shizuishan area, Ningxia, this study analyzes the geochemical indicators of selenium and available selenium in soil in the area.The results are as follows. The seleniumin soil in the study area is mainly originated from the black rock series in the Helan Mountain area, followed by siltation brought in by the agricultural irrigation water diverted from the Yellow River. The bioavailability of selenium in the study area is at a relatively high level, and the effective selenium enrichment and above covers 79.2% of the whole study area, with an area of about 777.2 km². The content of different forms of selenium is in the order ofresidualselenium>strongly organic matter-bound selenium>humic acid-bound selenium>ion exchangeableselenium≈water-soluble selenium > carbonate-bound selenium≈iron manganese oxide-boundselenium. The total selenium content is limited, while thewater-soluble selenium content is relatively high. The higher the total nitrogen and organic matter content in soil, the higher the total selenium and available selenium content. As the salt content in soil in the study area increases, the bioavailability of seleniumtends to gradually increase. The irrigation-silted soiland thefluvo-aquic soil with a pH value between 7.5 and 9 have moderate total selenium content and high available selenium content, and they are high-quality areas for planting selenium-rich agricultural products.