Excessive water is used by farm field in Tarim river basin, it is very important to deep study on the relation between area of farm field and natural vegetation in recent 50 years. Collecting and processing various decades of remote sensing data, and got area of farm field, grass, forest, town and non-serviceable field. These results indict that: Because of the high flow period between 1950 and 1972, a part of grassland converts forest. From 1972 to 1990, because of increase of farm field, limited water isn't enough to grassland and forest, and a fraction of forest area converts grassland again. With rapid increase of area of farm field, more water need from the river and underground, which causes water level depression, and natural ecology becomes deteriorative from 1990 to 2000. Comprehensive analysis indicts that agriculture control implemented by government is necessary to recovery of ecology, or farm field also would be lost eventually with destruction of natural ecology.