Plant can directly take up the intact amino acids, thus bypass the microbial mineralization of organic nitrogen. As an excellent carbon and nitrogen source, there exists competition for amino acid absorption between plant roots.and soil microorganisms. And the total flux of amino acids in soil may be enormous due to the extensive sources and short half-life. Studies on amino acid nitrogen nutritional contribution for plant by the technique of nitrogen isotopic tracer, has become a research topic in recent years ,which will help us better understand the principle of soil fertility. This paper summarized the recent researches on amino acid morphological characteristics in soil and its metabolic mechanism and nitrogen nutritional contribution for plant in different ecosystems, and discussed the present status and development trend of the amino acid circulation mechanism in the plant-soil-microorganism ecosystem and its bioavailability for plant. Finally, the topics of environmental regulating mechanism of amino acid bioavailability, amino acid carbon-nitrogen metabolism, and how to improve the field organic nitrogen management were all the core issues to be resolved.