Abstract: Google Earth is a satellite image browsing software, it provides a wide range of global image data by using “virtual earth” manner. Since its inception in 2005, its using group has been expaned, it can be used as a tool and software development platform in many applications.This paper explored the concrete steps and methods of secondary development by using the object-oriented programming language based on Google Earth, it provides a new way of thingking and methods to build a farm GIS system by using Google Earth.