Timely and accurate estimations of cotton field area at a national or provincial level are essential to management decisions of farmers and the government. As the China-Brazil Earth Resources Satellite (CBERS-1) was successfully launched in 1999, it is possible to monitor crops using remote sensing in the northwestern China's Xinjiang Uygur Autonomous Region and the cotton's annual acreage variation at a national level using remote sensing. A stratified sampling method is used to estimate the cotton field area in China and sampled data are collected by CBERS-1 images. Considering area of counties and crop fields is very different between the eastern and western China, different sampling units are used in the estimation. A 1∶250 00 standard map sheet (about 91 km²) is used as a sampling unit in the western China's Xinjiang Uygur Autonomous Region and one county is used as a sampling unit in eastern China. The sampling method is operationally used in the crop monitoring system for the Ministry of Agriculture.