Most of study on RAIM in the last few years has focused on the single satellite failure problem. However, if GPS, GLONASS, Galileo and other available satellite navigation systems are combined, or the satellite navigation systems are used in the civil navigation field, the assumption of single-satellite-failure is unreasonable. This paper analyses the maximum slope in the position error versus test statistic plot, which is very important for analyzing the RAIM availability. The simulation result shows that the simultaneous multiple faulty satellites will severely degrade RAIM availability. In the case of multiple satellites failure, the identification method used under the single satellite failure is ineffective. In order to solve this problem, this paper provides an approach for identifying the multiple faulty satellites. The simulation result indicates that the identifying method can exclude the multiple faulty satellites correctly.