Selenium (Se) is an essential trace element for humans and animals. Selenium deficiency can affect human health and lead to many diseases. It is a simple and effective way to supplement Se by eating Se enriched agricultural products. This paper systematically studied the effects of Se on human health, the daily Se intake by residents, the distribution of Se in soil and the characteristics of Se uptake by crops, the researches of Se-rich soils, the standards of Se-enriched agricultural products, and the safety assessment of Se intake from Se-enriched agricultural products. The necessity of developing the classification standard of selenium-rich soil was also described in this paper.