The present invention provides a global navigation satellite system (GNSS) based positioning system and tracking method using a data communication network. When a GNSS-based positioning device is connected to a data communication network, the positioning device transfers the GNSS digital data and supplementary information used for additional performance improvement to a location tracking server through the data communication network, the location tracking server calculates a position of the positioning device with improved receiver sensitivity based on plentiful computational resources available at the location tracking server. Thus, the positioning device may find its location of even in very poor signal condition. Further, the present invention provides a positioning system and method using a data communication network, which may achieve time synchronization when there is a need to extract not only position information but also absolute timing information.