Abstract: Stating the cultivation area of cereal crops in administrative unit and the spatial distribution information of cereal crops are not only the basis to estimate the food production, but also the important basis to constitute the food policy and adjust the planting structures. The spatial information technology represented by RS, GIS and GPS is the key technical support to state the cultivation area of cereal crops , and it is also the important part to achieve from conventional statistics to spatial statistics step by step. In order to obtain the planting area of corn by remote sensing measurement, this study chose Yuanyang county of Henan province where was the agricultural region with complex planting structure as experimental area and established field background database by high-resolution image. After the data was pretreated, the pre-classification was carried by the normalized difference vegetation index (NDVI) and digital number (DN) according to the multi-temporal thematic mapper (TM) images, and the planting range was preliminarily obtained. Then we integrated the classification results and vector field boundary, taking the area proportion of corn in the field as the delamination symbol to establish the delamination model, then we went out to investigate the real area proportion of corn in the selected field by the combination of remoting sensing images and vehicular GPS. By the GPS points, the corn pre-classification results were corrected using decision tree. At last, we used the investigated results as standard to judge the classification results, the position precision was 81.8%, and the gross precision was 91.1%. It shows that the position precision and gross precision of multi-temporal TM images can be improved by the database of field boundary.