Membrane　biofouling　is　a　challenge　for　biocarriers　facilitated　gravity-driven　membrane　(GDM)　systems　to　achieve　high-efficiency　filtration　in　decentralized　drinking　water　treatment.　The　purpose　of　this　study　was　to　investigate　the　effects　of　vacuum　ultraviolet　(VUV)　as　a　pretreatment　on　membrane　fouling,　permeate　water　quality　and　bacterial　communities.　VUV　pretreatment　was　found　to　significantly　reduce　the　cake　layer　resistance　by　24.4%　and　the　membrane　pore　resistance　by　40.0%　(p　＜　0.05),　resulting　in　a　22.2%　increase　in　stable　flux.　The　removal　of　low　molecular　weight　neutrals　and　protein-like　materials　was　enhanced　by　22.5%　and　40.1%　respectively　after　VUV　pretreatment.　The　heterogeneity　of　the　biofouling　layer　was　improved　by　VUV　pre-treatment,　and　the　porosity　and　roughness　were　increased　by　227.5%　and　46.5%,　respectively.　The　application　of　VUV　pretreatment　resulted　in　a　larger　nanoparticle　size　in　the　biofouling　layer　suspension　(peak　at　85.4　nm),　improvement　in　the　membrane　hydrophilicity,　and　a　decrease　in　protein-like　substances　adhesion.　The　richness　and　diversity　of　the　bacterial　community　were　decreased　by　VUV　pretreatment.　The　bacterial　community　structure　had　the　highest　mantel　correlation　with　biopolymers　(r　=　0.89).　Overall,　VUV　pretreatment　can　be　a　promising　strategy　to　effectively　alleviate　membrane　biofouling　in　biocarriers　facilitated　GDM　systems.