It is of great significance to study the nutrient transport and transformation mechanism between soil and products, and to establish the coupling relationship between the two elements, so as to improve the nutritional value of products. In this study, the "soil-millet" system of Qinghai Ping"an was taken as the research object, and the content of heavy metals and nutrients in soil and millet was determined, and the methods of standard comparison, grading evaluation and principal component analysis were used to evaluate soil quality, identify the nutritional function of millet, and analyze the nutrient source. The results showed that the soil in the study area was alkaline, the soil environment quality was good, the fertility was moderate, and it was naturally rich in selenium with high calcium, magnesium, strontium and other natural mineral resources. The heavy metals produced by millet were far lower than the national limit standard, and there was a synergistic absorption combination sequence of Mg-Mn-Cu-Zn-K-P in the process of nutrient accumulation. Millet is easy to gather Cu, K, Mg, P, Se and Zn elements.Strong ability to transport Cu, Mg, P, Se and Zn.The degree of Fe activation in soil was high, and the degree of Cd activation was low. Four nutrient lineages were identified in the nutrient source analysis, which were divided into basic nutrient sources such as Zn, Cu, Mg, Mn, K, and P, fortified nutrient sources such as Fe and Ca, and Se functional nutrient source and Sr functional nutrient source. The high-quality soil environment in the study area cultivates high-quality agricultural products, which are rich in Se, Fe, Cu, Mg, Mn and P, containing vitamin B1, folic acid ,Fe, Zn and K. It is a natural functional food for the human body to supplement mineral nutrients such as selenium, iron, copper, magnesium, and manganese, and can be vigorously promoted and applied.