Remote Sensing Application Centre (RSAC) has been working on monitoring the main crop cultivated areas as operational task and research project for several years.The main problems is that the time and features of background data used in sampling maybe produce system errors. The sampling method called stratified sampling adopted by RSAC is also used in this study. But there is an important difference that the background data used to stratify is the same year’s cultivated land data derived from an analysis result to MODIS data, containing crop cultivated area proportion information, instead of cultivated land data. The Area Proportion Enlargement Estimation (APEE) model designed in this study is different with Area Enlargement Estimation (AEE) adpoted by RSAC. The new APEE model was set up through calculating with twice weighted averaging. A case study limitedly presents the process of the sampling design and testifies feasibility of the method.