Abstract: Timely and accurate major crop plant area data has a great significance to the relevant departments and the development of agricultural production and rural policy. In this view, designing and implementation of crop plant area monitoring system based on .NET is necessary. The system uses three-tier C/S framework model, for scientific and advanced remote sensing techniques and statistical sampling techniques as the support, it can realize many functions such as the remote sensing image pre-processing, crop plant area monitoring, mass remote sensing data management, production web publishing and so on. The rigorous system testing and operation has been conducted, which proved that the system was stable and efficiency. It can be concluded that such system is widely useful for the relevant departments about agricultural statistics with timely data for decision-making support information.