It　is　necessary　to　evaluate　the　reliability　of　the　water　supply　network,　when　the　water　supply　network　is　damaged　by　an　earthquake.　Therefore,　this　paper　researched　the　feasibility　and　characteristics　of　the　surplus　power　entropy　as　the　reliability　index　of　the　water　supply　network,　and　established　a　scheme　framework　for　optimizing　and　improving　the　reliability　of　the　water　supply　network.　This　paper　developed　a　reliability　evaluation　model　for　the　water　supply　network　after　an　earthquake.　Combined　with　the　Monte　Carlo　stochastic　simulation　hydraulic　analysis,　this　model　is　also　based　on　the　pressure-driven　nodes　water　demand　model.　In　the　case　study,　the　surplus　power　entropy　method　was　applied　to　test　the　reliability　of　the　model.　The　statistical　curves　of　the　surplus　power　entropy　of　nodes　and　pipe　networks,　the　distribution　of　the　surplus　power　entropy　with　different　intensities　in　pipe　networks,　and　the　comparison　results　of　three　reliability　improvement　schemes,　before　and　after,　were　obtained.　The　influence　factors　of　the　surplus　power　entropy　were　obtained　from　the　data　analysis.　The　high　consistency　between　the　surplus　power　entropy　and　flow　entropy　verifies　the　feasibility　of　the　surplus　power　entropy　as　a　reliability　index.　The　three　schemes　show　that　the　surplus　power　entropy　index　can　be　used　as　a　beneficial　supplement　to　the　reliability　evaluation　index　of　the　pipe　network.