Abstract: A safety assessment model is established based on the analysis of fuzzy fault-tree,and an safety assessment method for ship launching in the following aspects:minimum cut sets analysis, evaluation of failure probability of the top event and fuzzy importance analysis of the basic events. In present paper, the basic principle of fuzzy fault-tree is introduced, and an example of fuzzy fault-tree analysis of one top event in a 4300 PCTC ship launching on longitudinal slide way is given and illuminated.