Traditional global navigation satellite systems (GNSS) based on vector tracking (VT) have various structures. However, some GNSS measurements have no connection with the dynamic of the user when the loop loses lock in the shade, e.g. urban canyon, tree shade, etc. To improve the navigation accuracy in a weak environment, a distributed GNSS/inertial navigation system (INS) integrated navigation system based on VT is proposed. The change in the pseudo-range rate and pseudo-range from the loop is employed in the GNSS receiver. The reliable navigation results can be output from a distributed navigation filter according to effective GNSS measurements and modified INS information. The field test shows that the proposed distributed GNSS/INS navigation system can achieve reliable navigation in weak signal environments.