To meet the needs of modern agricultural machinery management, an agricultural machinery trace monitoring system based on the technology of GPS, GPRS and Google Maps was developed in order to realize the real-time monitoring and scheduling of farm machinery. This system with built-in GPS and GPRS modules, which use wireless network transfer GPS data to remote machine by single-chip microcomputer. With Google Maps API, a Web GIS system was established. An agricultural machinery management by ASP.NET was achieved. Web Service and Ajax technology was used to do such things like trace playback, length measuring, and calculation of land area function.