In　this　article,　for　the　Linux　operating　system　environment,　with　the　characteristics　of　ambiguity　and　uncertainty　for　the　occurrence　probability　of　system　failures,　fuzzy　theory　is　introduced　into　the　fault　tree　analysis.　The　occurrence　probability　of　basic　events　in　the　conventional　fault　tree　is　made　fuzzy　by　introducing　the　concept　of　fuzzy　sets.　Using　the　upstream　method　for　solving　the　minimum　cut　sets　and　transferring　the　different　fuzzy　numbers　into　triangular　fuzzy　numbers,　the　method　is　validated　with　the　CPU　error　detection.　This　way　provides　a　theoretical　basis　and　implementation　for　system　reliability　evaluation,　fault　diagnosis　and　maintenance　decisions.　©　2012　IEEE.