Abstract: In the past 30 years，intensive human activities produced a series of ecological problems in the Manas River Basin，especially excessive expansion of arable land and degradation of woodland and grassland，which threaten the ecological security of oasis. Based on remote sensing image data，this paper studied the characteristics of land use change of a typical oasis area in the Manas River Basin—Shawan County and Eighth Agricultural Division of the Xinjiang Production and Construction Corps. Then spatial land suitability was evaluated quantitively by using GIS. Finally，Cellular Automata model was built by constraints of suitability evaluation results and the “returning cultivated land to woodland and grassland” policy for spatial optimizing. Results showed as follows：（1）expansion of cultivated land was significantly from 1976 to 2012 that mainly converted from unused land，woodland and grassland; net area of woodland reduced 9.035×10⁴ hm² and 57.92% of reduced woodland was conversed to cultivated land; despite a 5.621×10³ hm² net increase in the study period，6.352×10⁴ hm²  grassland converted to cultivated land； water area reduced with 1.198×104 hm2 and rural residential area grown nearly 3.5 times than that in 1976； unused land area reduced 2.441×10⁵ hm² that mainly converted to arable land，grassland and woodland. （2）the area of cultivated land，woodland and grassland in Class I （very appropriate） and II level （appropriate） of land suitability evaluation，respectively，accounted for 79.74%，70.23% and 59.82% of the total study area；（3）the proportion of cultivated land，woodland and grassland turned from 6.04∶0.39∶3.57 to 4.03∶0.99∶4.98 after the optimization. Optimized results showed a restraint of the arable land expansion，and increased the proportion of woodland，grassland which is conducive to stability and sustainable socio-economic-ecological development of the oasis region.

Key words: the Manas River Basin, oasis, land suitability, spatial optimizing, cellular automaton