Abstract: Precise diagnosis of degradation of a regional ecological system by degree with its driving factors specified is the precondition and basis for efficient implementation of ecological restoration. Based on the prevailing theories for diagnosis of ecological degradation, it has been pointed out that ecological degradation is a relative concept and that determination of a reference system and an index system is an essential step for the diagnosis. The determination of a reference system for the diagnosis shows that for diagnosis of degradation of a regional ecosystem should not focus on just one specific historical status, but rather pay more attention to temporal dynamics and spatial variability of the degradation, so as, to ensure objectivity of the diagnosis. On such a basis, to highlight the close relationship between ecological degradation and ecological functions as well as the comprehensiveness of ecosystem degeneration in important ecological function areas, a train of thought and a flowchart for diagnosis of ecological degradation from the perspective of ecological maintaining ability, ecological self-restoration ability and ecological pressure have been brought forth, and an index system for the diagnosis has been set up. In order to embody the comprehensiveness and hierarchy of ecological degradation diagnosis, single factor analyses, including ecological function maintain index (EMI), ecological resilience index (ERI) and ecological pressure index (EPI), is combined with comprehensive analysis, and an integrated index for determining ecological degradation is set up for comprehensively diagnosis degree, which may provide some theoretical guidance and technical support for higher precision of the diagnosis of ecological degradation.