The invention discloses a new method for RAIM (
receiver autonomous integrity monitoring) based on a 
satellite selecting 
algorithm in a multimode 
satellite navigation system. The method comprises the steps of first determining space position information of satellites according to a navigation message and eliminating satellites with a small 
elevation angle according to a shielding angle; determining an 
observation matrix including only one 
clock correction item according to 
clock correction conversion factors in the navigation message; selecting p satellites from N visible satellites so as to be used for positioning calculation of a 
receiver, acquiring a 
satellite combination, which enables the GDOP (geometric 
dilution of precision) to be minimum, through the satellite selecting 
algorithm to act as calculating satellites, and determining a weight matrix in WLS (weighted 
least squares) according to parameters such as the carrier-to-
noise ratio, the 
loop bandwidth, pre-check integral time and the like of satellite signals; carrying out RAIM availability detection according to a 
false alarm rate and a missed alarm rate which are preset by the 
receiver, and calculating a pseudo-range residual error threshold value after positioning according to the 
false alarm rate and a degree of freedom in Chi-squared distribution; carrying out global detection at first, then carrying out local monitoring in a circumstance that a fault satellite exists, determining calculation satellites again through satellite selection, and finally carrying out positioning calculation through selecting satellite combinations within the threshold value. The method disclosed by the invention is simple, high in 
fault recognition rate, not only applicable to multi-mode and multi-fault 
satellite navigation systems, but also applicable to single-mode and multi-fault 
satellite navigation systems, thereby providing new ideas for carrying out RAIM by a modern GNSS (global navigation 
satellite system).