Abstract:   GPS-RTK as a method of improving positioning accuracy in Global Positioning System (GPS) measurement technology has been widely promoted and used. Nowadays, BeiDou satellite navigation system (BDS) has been built regional-navigation constellation.BDS has been officially provided for continuous passive positioning, navigation, timing and other services. However, due to the shortcomings of BDS single constellation positioning, resulting in low positioning accuracy. So multi-frequency multi-system integration navigation and positioning has become a new hot spot for navigation and positioning research. This paper introduces RTK technology and the application of double-difference RTK in GPS+BDS system. It also points out the advantages of double-difference RTK in geographical information collection system and the problems in practical application. It provides some useful reference value for similar engineering applications.