This　paper　introduces　an　efficient　methodology　for　evaluating　the　first　four　central　moments　of　performance　functions　in　structural　reliability　assessment.　The　procedure　of　the　proposed　method　is　divided　into　three　major　steps.　First,　a　performance　function　is　approximated　as　the　sum　of　univariate　and　bivariate　functions　by　the　bivariate　dimension-reduction　method.　Next,　a　new　criterion　based　on　importance　measure　analysis　is　proposed　for　dividing　the　bivariate　functions　into　significant　bivariate　functions　and　non-significant　bivariate　functions,　and　then　the　new　approximation　of　the　performance　function　is　obtained.　Finally,　formulas　are　derived　for　evaluating　the　first　four　central　moments　of　the　proposed　performance　function,　in　which　the　first　four　raw　moments　of　the　univariate　and　bivariate　functions　can　be　achieved　by　a　point　estimating　method　in　a　standard　normal　space.　The　effectiveness　and　efficiency　of　the　proposed　method　are　demonstrated　through　three　numerical　examples.