Substantial　volumes　of　hazardous　shale　gas　produced　water　(SGPW)　generated　in　unconventional　natural　gas　exploration.　Membrane　distillation　(MD)　is　a　promising　approach　for　SGPW　desalination,　while　membrane　fouling,　wetting,　and　permeate　deterioration　restrict　MD　application.　The　integration　of　gravity-driven　membrane　(GDM)　with　MD　process　was　proposed　to　improve　MD　performance,　and　different　pretreatment　methods　(i.　e.,　oxidation,　coagulation,　and　granular　filtration)　were　systematically　investigated.　Results　showed　that　pretreatment　released　GDM　fouling　and　improved　permeate　quality　by　enrich　certain　microbes＇　community　(e.g.,　Proteobacteria　and　Nitrosomonadaceae),　greatly　ensured　the　efficient　desalination　of　MD.　Pretreatment　greatly　influences　GDM　fouling　layer　morphology,　leading　to　different　flux　performance.　Thick/rough/hydrophilic　fouling　layer　formed　after　coagulation,　and　thin/loose　fouling　layer　formed　after　silica　sand　filtration　improved　GDM　flux　by　2.92　and　1.9　times,　respectively.　Moreover,　the　beneficial　utilization　of　adsorption-biodegradation　effects　significantly　enhanced　GDM　permeate　quality.　100　%　of　ammonia　and　53.99　%　of　UV254　were　efficiently　removed　after　zeolite　filtration-GDM　and　granular　activated　carbon　filtration-GDM,　respectively.　Compared　to　the　surged　conductivity　(41.29　mu　S/cm)　and　severe　flux　decline　(＞82　%)　under　water　recovery　rate　of　75　%　observed　in　single　MD　for　SGPW　treatment,　GDM　economically　controlled　permeate　conductivity　(1.39-19.9　mu　S/　cm)　and　MD　fouling　(flux　decline=8.3　%-27.5　%).　Exploring　the　mechanisms,　the　GDM-MD　process　has　similarity　with　Janus　MD　membrane　in　SGPW　treatment,　significantly　reduced　MD　fouling　and　wetting.