Abstract: Method of Network RTK based on undifferenced observation corrections allows clients to gain rapid and precise positioning service in undifferenced processing mode equivalent to Network RTK by providing error corrections of each satellite. Compared with current Network RTK, the new method could efficiently solve problems of ambiguity re-initialization caused by selected main reference stations change under circumstances of cross reference sub-networks within the same CORS network, or even cross different CORS networks, thus providing continuous and reliable positioning results for clients during observing session, as well as seamless link of Cross-CORS service. In addition, based on the characteristics of realizing Network RTK technology under the undifferenced processing mode, this new method makes the unification of regional Network RTK and wide-area undifferenced precise positioning technology possible. Through serial analysis of a practical example, this paper testifies the consistency in positioning accuracy, and initializing time of this new method and the current Network RTK, together with the efficiency of this method to provide seamless link of different reference sub-network and Cross-CORS service.