B-values analysis and processing in multiple reference consistency check is critical for integrity monitoring of GNSS landing system. Considering the problems of the traditional processing method that it is not sensitive to the sources of failure and it is difficult to judge whether the failure comes from the satellite or the receiver, we studied the improved B-values fault detection algorithm based on C-values. The new processing method uses the rule of maximum likelihood estimation, and by fabricating C-values based on satellite data, setting up the relevant threshold values, and analyzing and comparing the variation of C-values, it can make comprehensive analysis to the possible failures based on B-values processing. Experiments show that the new processing method is very effective in fault analysis, especially for satellite faults. Besides, it also improves the level of system availability.