Abstract: Intensifying the researches on degraded ecosystem has been faced as pressing problem in China.In this paper,the factors of ecosystem degradation were analyzed,degraded processes and characteristics of ecosystem were expounded, and some problems about restoration and rehabilitation also were discussed. Disturbance induced by human has been the main force of degradation. According to the disturbance regimes and behaves of degradation, processes of ecosystem degradation have several models, namely, sudden degradation course, leap degradation course, gradual degradation course, continual degradation course and compex of several courses. For example, according to degraded extent the gradual degradation course could be divided into four steps with different degradation characteristics including biodiversity loss and declining, structural simplification, disintegration of food web,open of substance recycles, productivity decline,abnormality and some troubles of energy flow, losing or weakening abilities of environmental protection, and lowering of system stability . Based on differences of degradation processes and extent,the restoration and rehabilitation on different degraded ecosystem should have verious countermeasures. The restoration of biodiversity and system structure is the key and pathways of rehabilitation and restoration of the degradaed ecosystem.

Key words: Bt corn, Cry1Ab protein, rhizosphere soil, straw return, degradation in field, simulation model.