Two kinds of the deficiencies exist in the traditional dam reliability and the safety coefficient calculation methods. First, it is impossible to give accurate mean to design variable in case study, because to large extent, means are greatly influenced by many objective factors or man-made effects, which degree of effects has greater degree of ambiguity. Second, the traditional reliability theory takes zero point as measure of dam’s failure or not, and on both sides of zero point the structure of state mutants from security to failure. But in fact, it’s very hard to give a definite limitation to the dam state from security to failure, because a fuzzy scope exists between stability and failure. On the basis of solving the above two issues, this paper for the first time applies fuzzy reliability theory to the stability research of tailings dam under earthquake action , considering fuzziness of both the event of tailings dam failure and the main variables and parameter. Integrating fuzziness and randomness, this paper explores fuzzy random reliability analysis methods of tailings dam engineering. The results of case study show that the calculation results agree well with the actual situation, this analysis method is more scientific and reasonable than traditional dam safety factor calculation method, and better reflects the real situation. It also provides a new way to calculate stability of tailing dam considering earthquake action.