Abstract: Seepage failure is one of the main failure modes in earth dams. Based on indeterministic analysis of the seepage risk, this paper put forward the seepage failure risk mode with the fuzziness of parameters in the design and the expectation of the dam' s effective working life limit. Furthermore, the Monte Carlo Method based on MATLAB was used to work out risk probability. Taking into account the fuzziness risk analysis on seepage failure made the result of calculation on the risk closer to the reality. When all the fuzzy parameters are made fuzzy, available traditional methods in calculating the risk can be used directly to work out the probability of the failure.