The　layout　of　city　pipelines　is　usually　called　a　pipe　network.　In　order　to　evaluate　the　seismic　resistance　of　a　pipe　network,　the　source　to　terminal　(s-t)　reliability　algorithm　is　mostly　used.　The　exact　reliability　computation　method　of　s-t　problem　is　extremely　time-consuming.　It　is,　as　an　algorithmic　problem,　classed　in　the　NP　hard　family.　For　a　large　pipe　network,　approximate　computation　methods　are　generally　attractive.　One　feasible　approximation　approach　is　to　use　bounds,　and　another　is　to　use　simulation.　This　paper　presents　a　directly　disjoint　algorithm　using　bounds　for　seismic　reliability　evaluation　of　pipe　networks.　Based　on　the　principle　of　breadth-first　search　and　minimal-distance-first　search,　the　proposed　algorithm　could　obtain　exact　solution　of　simple　networks　and　approximation　of　large　networks　with　real-time　accumulation　of　disjoint　minimal　paths　and　cuts.　Compared　with　the　Modified　Dotson　algorithm,　this　algorithm　is　faster　in　solving　the　connective　reliability　of　pipeline　network　with　low　element　operation　probability.　Compared　with　the　Minimal　Cut-Based　Recursive　Decomposition　algorithm,　a　more　optimum　disjoint　set　can　be　solved　by　this　algorithm.　At　the　end　of　this　paper,　the　proposed　algorithm　was　used　to　estimate　the　seismic　reliability　of　a　water　supply　network.　©　2011　ASCE.