Abstract: As a part of the study of Keshan disease and kaschin-Beck's disease are associated with geographical environment, We have collected 236 soil samples from various natural zones in China and analysed their selenium content by fluorence spectropotometry.The frequency of se-content in the soils mainly shows a logarithmicnormal distributions, so geometric average is adopted in this research work. The results obtained are as follows.1. The average Se-content in the soils in China is 0.16 ppm, that is, lower than the mean Se leve in the soil of the world.2. The geographical distribution of the Se content in the soils shows a beltformal regional differentiation. The belt, that consists of dark-brown forest soil, black soil, drab soil, dark Loessial Soil, purple soil, Alpine-and Sub-alpine meadowsoil,is a low selenium zone of soil running from northeast to southwest in China. The average Se contents in the soils in this belt range from 0.06 to 0.12PPm. So there are other two belts in the Northwest and the Southeast on both sides of the low selenium zone, and their average Se contents in the soils range from 0.11 PPm to 0.32 PPm. This situation of the soil Se geographical distribution is similar to that for the grains and also for the human hairs.3. In the Northwest belt with arid and semiarid features, the Se contentsof soils in the eluvial landscape in the mountains are lower than that in the subordinate landscape in the basins and the flood-fan deltas. It indicates that the activity of selenium in alkaline environment is higher. In the red-Yellow soil zone in the Southeast, on the contrary, the Se contents of soils on mountains and hills are higher than in the fluvial plains. It indicates the Se-accumulation in the re-yellow soil.4. Within the low selenium zone, the Se contents in the Black soil and Dark-brown forest soil are higher than in the drab soil, dark loessial soil and purple soil. The Se contents in the soils on the mountains, hills and high plains are lower than the Se contents in the cultivated fluviogenic soil on the plains and fluvial terraces.5. The low selenium soil zone corresponds to the regionswh ere the keshan disease and Kaschin-Beck's disease in man and white Muscle disease in animal occur. The difference of the soil Se contents between the disease region and the nondisease region is significant statistically. It Shows that the low selenium content in the soils is the one of the basic factors leading to low Se content in the grains and therefore the occurrence of the disease in low selenium regions.Finally, the paper also discussed the factors, which influence the distribution of Se in soils, and the possibility of increasing the Se content in the grain by improving the soil to prevent the disease.