Cadmium (Cadmium, Cd), as one of the major heavy metal pollutants in soil in China, poses a serious threat to soil ecosystems, plant growth, and human health. Nano selenium (Nano Selenium, Se NPs), due to their unique physicochemical properties and excellent biological activities, have become a research hotspot in alleviating soil Cd pollution. This article systematically summarizes the sources and hazards of soil Cd, deeply explores the effects and intrinsic mechanism of Se NPs in alleviating Cd stress in plants, and simultaneously analyzes the advantages and disadvantages of different Se NPs preparation technologies. Future research should focus on optimizing green and low-cost preparation technologies, further revealing the mechanism of Se NPs in the soil-plant-microbe system, exploring the synergistic effects with other remediation technologies, and strengthening the systematic assessment of environmental risks to promote their sustainable application in the remediation of agricultural Cd pollution.