Ground Based Augmentation System (GBAS) can strongly support aircraft’s precise approach landing,and integrity monitoring is not only the difficulty of the system realization but also the key point to safeguard the flight.The ionosphere grads is the uppermost element that influence the GBAS integrity.Several algorithms are used together to achieve the ionosphere grads monitoring and ensure the ionosphere grads in an acceptable limit,ultimately guarantee GBAS integrity.In this paper,the theory basis of the ionosphere grads monitoring algorithm is analyzed firstly,then an improved algorithm is proposed,which can increase ionosphere grads monitoring sensitivity effectively.The comparable experimental analysis of present and improved algorithm is given; the results show that multi-monitoring algorithm can monitor ionosphere grads from different aspects,while the improved algorithm can increase monitoring effect apparently.