Abstract: Fault tree analysis on existing models can not solve complex environment of multiple uncertainties，the use of the random fuzzy variables primitive opportunity to propose a random fuzzy fault tree top incident primitive opportunities algorithm.The basic idea of this algorithm is to first go through fuzzy simulation to produce a group of fuzzy numbers which satisfied with the requirement，and then use these fuzzy numbers as parameters carry through random simulation to achieve the primitive opportunity of top event.Finally，examples show that the algorithm in solving the problem of double fuzzy uncertainty than any fault tree algorithm has advantages.