Selenium (Se) is an essential trace element for humans. The relationship between Se nutrition and health has always been a hot research field. There is a low-Se belt in the natural environment of China, which extends from northeast to southwest of the country. Since the 1980s, with the socioeconomic development, the Se nutrition level of the population within this belt has been obviously improved. The time-space difference of the corresponding soil-grain-human hair Se level changes is worth a systemic study.