Abstract: Ecologists have not reached a consensus on the major issues in ecosystem health. In this paper, three concepts relating to ecosystem health, i.e., ‘h
ealth’, ‘system’ and ‘ecosystem’, were analyzed, and the concepts and connotations of ecosystem health, its research significances, content framework, and feasible scales, as well as the diagnosis and grade-assessment of ecosystem quality were discussed. It is suggested that ecosystem is one of the special systems in the context of systems science, with the characteristics of integrity, stability, and sustainability. Good integrity, stability, and sustainability are the necessary and sufficient conditions of ecosystem health. The criteria of ecosystem quality include qualitative diagnostic and grade-assessment ones. The qualitative diagnosis is a fact judgment (yes or not), while the gradeassessment is a value judgment. The indices for grade-assessment of ecosystem quality
could also be divided into two kinds, the restrictively comparable and the non-restrictively comparable. The complexity of ecosystem determines that the studies on ecosystem health should be made with the help of the theories and methods in systems science and nonlinear science, the time lag in ecosystem disease deter
mines that the forecast and early warning of ecosystem health should be strengthened, and the transdisciplinarity of ecosystem health research determines that t
he reseds needs a broad cooperation among ecological, environmental, medical, social, and economic scientists.

Key words: Arable soil, Dissolved organic matter, Hydrophilic, Biodegradable, Vertical fractionation