Abstract: Safety analysis on primary confinement of tritium processing system for TBM was carried out with Preliminary Hazard Analysis.Firstly,the basic PHA process was given.Then the function and safe measures with multiple confinements about tritium system were described and analyzed briefly,dividing the two kinds of boundaries of tritium transferring through,that are multiple confinement systems division and fluid loops division.Analysis on tritium releasing is the key of PHA.Besides,PHA table about tritium releasing was put forward,the causes and harmful results being analyzed,and the safety measures were put forward also.On the basis of PHA,several kinds of typical accidents were supposed to be further analyzed.And 8 factors influencing the tritium safety were analyzed,laying the foundation of evaluating quantitatively the safety grade of various nuclear facilities.