Abstract: Based on the emergy models, the authors assess the succession and sustainability of the agro-ecosystem of Huang-Huai-Hai plain in China during the past 17 years. Results show that the emergy production of the fishy subsystem and the livestock subsystem are growing subsystem while two producing subsystems and total emergy production of the systems will decline with the emergy inputs increasing. Likewise all kinds of emergy efficiency will decrease. The discussion of emergy indicators indicates as follows: the development of the system tends to the dependence on fossil-energy and economy resource gradually, the investment ratio (EIR) tends to increase; the emergy yield ratio remains to decrease but is higher than 1 and the Chinese Average (0.75), thereby the total emergy production of the system reaches 1.856×1024Sej in 2000 with being equivalent to 3.640×1011EM and overtopping total value of agriculture production 6.410×1010; Environmental loading ratio remains increased, and reaches 3.79 in 2000, which equals to the level of the moderately developed countries and is higher than the Chinese Average (2.8); Environmental sustainability index gradually declines. At last, the suggestion is put forward to optimize agro-ecosystem function and improve the sustainability of the system by increasing the application of organic fertilizer and cultivating the diversity of the animal and plant.