Abstract: Based on the theory of H ∞ robust filter, a tightly integrated GPS/INS system is presented using H ∞ filter. The variable state includes position error, velocity error and attitude error and measurement is composed of pseudorange, pseudorange rate and carrier phase. In order to improve the robust of the complete integrated navigation system, H ∞ robust filter is adopted. The dynamic simulation is carried out and the result shows that the simplified system can work with better precision and excellent robustness. The scheme can put into practice easily.