Abstract: Quantitative analysis and evaluation of the agro-ecosystem of Aba, Sichuan Province, were conducted on the basis of emergy theory. Based on the results, there is an increase in total emergy input from 1.126 × 10²² to 1.661 × 10²² sej·a^-1, with an observed increase in total emergy output from 5.002 × 10²⁰ to 1.383 × 10²² sej·a^-1 for 1952 ~ 2005. Ecological function potential drops from 54.08% to 37.02% and the basic population capacity increases from 199 400 to 315 100. Emergy self-support ratio drops from 74.58% to 54.13%, while emergy investment ratio increases from 34.0% to 85.0%. Emergy density increases from 1.34 × 10¹¹ to 1.97 × 10¹¹ sej·m^-2 and emergy/money ratio decreases from 4.93 × 10¹⁴ to 1.81 × 10¹³ sej·^-1. There is an increase in environment load ratio and net energy yield ratio from 0.85 to 1.70 and from 0.18 to 1.82 respectively. Sustainable development index increases from 0.20 to 1.07. The results therefore indicate a continuous increase in agro-ecosystem production efficiency in Aba. Eco-tourism plays an important role in the development of the system. However, an unsustainability risk of the system exists due to insufficient input of industry-assisted emergy and over-consumption of natural resources. From the discussions above, it is important that sustainable development agro-ecosystem should be promoted in Aba.