Abstract: The dynamics and magnitude of assets and debts of oasis agro-ecosystems in Liangzhou District, Gansu Province were analyzed for the period of 1949~2005. The analysis explored sustainable development capacity and predicted future oasis agro- ecosystem development in Northwest China. The results show a rapid decline in the environmental assets of the agro-ecosystem from 1949 to 1970, dropping on the average from 14.14 to 4.93, which is 65.13% reduction. There is also a slow increment to 33.33 from 1970 to 2005. A steady negative growth exists in environmental debt from -0.91 to -56.67, increasing 62.27 times from 1949 to 2005. Net environmental assets exhibit a decreasing/increasing trend for the period under study. Environmental assets are strategic, gradually driving weakening asset surplus from 1949 to 1970, and dropping to zero in the 1970. Since 1970, debts have become dominant in the oasis agro-ecosystem, leading to asset deficit that has gradually increased, especially in the late 1980s. However, the situation begins to improve after 2000. The asset/debt table in 2005 shows that among 30 source indexes of livelihood, development, environment, society and intelligence supporting systems of sustainable development ability, 10 are in the asset column, 17 in the debt column, with a net asset of -23.34 for Liangzhou agro-ecosystem. The study shows that economic development in Liangzhou District is far from sustainable, however, environmental asset storage of the agro-ecosystem is lately improving. This implies that economic development in the region is transforming from a non-sustainable to a sustainable mode.