The degradation of ecosystems was discussed from a view of eco mechanics in thi s paperIt was suggested that any ecosystem could be regarded as a kind of the substance integration with three dimension spatial structure, and that it also had a property of "movement" which referred to the displacement of the state, but not the c hange of the place of ecosystem Actually, the degradation of ecosystem was a p rocess of ecological movement from a high level or stable state to an imbalance state Any ecosystem had a certain eco mass and eco inertia When the result ant of eco forces produced by human and natural disturbance exceeded their inhe rent ecological resistance force, ecosystems would take movement or displacement  This paper also presented a quantitative expression for calculating the poten tial of ecosystem degradation with four indices, including the eco mass index ( EMI), the natural disturbance index (NDI).