JC　method　is　in　common　use　in　the　structure　reliability　analysis.　In　this　paper,　the　program　which　can　be　used　as　to　consider　the　truncated　distribution　has　been　proposed,　With　this　method　the　reliability　index　is　more　closed　to　the　practical　engineering.　The　program　also　can　be　used　as　to　deal　with　the　non-convergence　in　the　iterative　process.　In　the　example　of　gravity　dam,　we　have　calculated　the　varied　reliability　index　which　come　from　the　truncated　distribution,　type　of　distribution　and　the　variable　variance.　The　result　can　be　referenced　in　design　of　the　hydraulic　structures.