Aiming at problem that traditional receiver autonomous integrity monitoring（ RAIM） algorithms have a low detection and exclusion rate for 15

50 m level small faults

and are difficult to satisfy the application in multiranging faults scenarios

set up four typical models of geometry structure of satellite distribution

and through studing impact of model on the coupling between positioning error brought by ranging with deviation and detection statistics

present an enhanced RAIM algorithm based on optimal geometry grouping. The novel algorithm

which is based on hypothesis test

establishes new detection statistics and thresholds by using the residual vector of groups

then detect and exclude ranging with deviation by

testing the consistency of subsets. Simulations show that

the proposed algorithm can promote detection and exclusion rate for small faults

improve performance of RAIM

and support hypothesis of single-ranging fault or multi-ranging fault scenarios of combined navigation system effectively reduce estimated location error and guarantee precision of positioning solution.