Selenium (Se) is an essential micronutrient for human health, and it plays an important role in selenoproteins by forming the active site as selenocysteine. Plant foods provide the main sources of Se for human beings. However, the average daily Se intake is oftentimes insufficient to meet the requirements of human health required for protection against cancer, cardiovascular diseases, and other severe infectious diseases. Soybean (Glycine max L.) is an important oil crop in the world, especially with a protein content as high as 35%–40%. Soybean seeds are often cultivated into bean sprouts or processed into soy milk, tofu, and beancurd sticks for people to eat. Therefore, increasing the Se content of soybean seeds is of great significance for improving daily Se intake. People can improve Se content in soybeans by improving cultivation techniques and applying Se to soil and plants. However, Se applied to the soil by mixing with chemical fertilizers is readily fixed and lost, resulting in a low utilization efficiency. In contrast, foliar spraying of Se was postulated to be more effective for increasing Se concentration in soybean seeds without experiencing negative effects within the soil profile.