Abstract: Estimating winter wheat planting area using remote sensing imagery is the basis for estimating winter wheat yield. This research deals with the estimation of planting area of winter wheat in Huantai County, Shandong Province, based on Landsat ETM+ imagery. Image segmentation was done after data preprocessing, then knowledge-based object oriented classification was conducted to extract wheat area information. Accuracy assessment proves that ideal classification results can be obtained, the area-estimating error of the whole study area is –111 hm2, and the largest area- estimating error in Guoli County is 95hm2, which can meet the requirement of application.