Abstract: Based on the ease study of national ecological demonstration area of Yuexi Co unty，a set of quantified indicator system and two kinds of mathematical methods(indices weighed coupling method and fuzzy comprehensive evaluation method)are developed and explained in detail for calculating and evaluating the development sustainability in multi-temporal-spatial scales．The results show that in datum year(2000)，near future year(2005)and long-term target year(2010)，the sustainability degrees are 0．268，0．541，0.859 respectively，among which the best memberships are unsustainability (0.487)，preliminary sustainability(0.484)and sustainability(0．663)respectively；in addition，the sustainability degreesand memberships of natural subsystem are always the best among three target years．This is dovetailed with the present condition and future trend of this studied region，such as predominant environment and resources ，under-developed economy and good po tentiality．It will efficiently promote the areal sustainable development if the plan can be implemented on time．