Abstract: The problem of complexity in calculation presents to fault tree analysis.Binary decision diagram is a new method in solving the problem.The ordering of the basic event is a crucial problem in fault tree being transferred to binary decision diagram，which is an NP problem.A heuristic algorithm of transferring fault tree to binary decision diagram is presented.The ordering of the basic event is avoided in the algorithm.The structure of the fault tree is taken into account in the algorithm in order to ensure the simpleness of binary decision diagram.