Abstract: It was proved that the new-high-moisture-material is perfect packing material beside roadway because of its early strength，easy pump-ability，good goaf-tightness，etc. Due to various reasons，the new high-moisture-material backfilling system sometimes goes wrong. Its fault decreases the backfilling efficiency. Based on the actual failure data of Qiuji mine backfilling system，research and analyze the reliability of the backfilling system by using the fault tree analysis(FTA).The results show that the reliability of the system is 0.9235,and it can maintain the production requirement. Preventing mis-operation and regularly maintaining the equipment are the effective ways of improving the reliability of the system.

Key words: New high-moisture-material, Retaining roadway along gob, Reliability, FTA