An ultra-tightly coupled model and a method for controlling replica signals generation in the tracking loop are proposed based on the analysis of various ultra-tight GPS/INS integration model. Moreover, the intrinsic relationships between the loop measurements and INS navigation solutions in an ultra-tight GPS/INS Integration model are analyzed and demonstrated. Finally, the coupling experiments are carried out, and the experiment results indicate that there is an intrinsic relationship and a deep fusion mechanism between tracking loop measurements and INS navigation solutions in an ultra-tight GPS/INS integration model.