The purpose of the paper is to analyze the main factors that affect TBM availability. In the paper, the characteristics of the surrounding rock and the 2 100 mlong boring record of Lingbei tunnel of Hanjiang RiverWeihe River Water Conveyance Project are analyzed, the factors causing the abnormal downtime of TBM are determined, the fault tree model for the abnormal downtime of TBM is established. The results show that the mucking system failure, support equipment failure, cutter head and cutter failure and electric power failure are the main factors leading to the low availability of TBM. The correlation between TBM availability in fractured rock mass conditions and Field Penetration Index (FPI) is analyzed. The results show that there is no obvious correlation between TBM availability and FPI, while the mucking system failure, support equipment failure and cutter head and cutter failure have strong correlation with FPI. The main causes for the failures are analyzed and countermeasures in terms of equipment management and construction management are proposed.