The invention belongs to the technical field of satellite navigation positioning, and particularly relates to an integrity risk probability distribution method supporting a satellite navigation positioning reliability requirement. The method comprises steps of according to navigation performance required in different navigation applications, establishing fault tree modules for integrity risk sources in different applications; according to the Bayes rule, finishing an optimal distribution scheme of the integrity risk probability; establishing an one order Markov switching module for each main integrity risk source, according to a specific integrity risk source, setting an initial condition and prior information of the module, and finally determining the P; and determining a sigma expansion coefficient subset according to counting features on positioning errors imposed by specific integrity risk sources in different applications. According to the invention, an improved sigma expansion algorithm based on the expansion coefficient set is provided and expansion coefficients are determined, so theoretical basis is provided for ideal error hypothesis required by integrity monitoring; and a minimal protection level is finally designed, so the requirement of high reliability of satellite navigation positioning is met.