Waste　sludge　is　a　typical　solid　waste　generated　during　construction　excavation,　which　needs　innocuity　treatment　and　resource　utilization.　The　development　of　geopolymer　pavement　base　material　using　waste　sludge　is　an　economic　and　environmental　method　to　realize　the　utilization　of　waste　sludge.　This　manuscript　aims　to　develop　a　geopolymer　pavement　base　material　using　waste　sludge　and　further　evaluate　its　water　stability　under　water　soaking　environment.　The　geopolymer　specimens　with　different　slag　and　waste　sludge　contents　were　prepared.　The　optimum　mix　proportion　of　geopolymer　was　determined　by　analyzing　the　effect　of　slag　content　on　the　ultimate　compressive　strength　(UCS)　and　elastic　modulus.　The　CO2　emissions　and　energy　consumption　of　geopolymer　was　analyzed.　The　water　stability　of　the　geopolymer　was　further　evaluated　by　analyzing　the　effects　of　soaking　time　on　the　density,　wave　velocity,　mechanical　properties　and　pore　structure.　The　results　show　that　the　geopolymer　with　50%　slag　content　has　the　largest　UCS　and　excellent　strength　development　characteristics.　The　UCS　of　geopolymer　pavement　base　material　reaches　48.4　MPa　and　the　CO2　emissions　and　energy　consumption　were　reduced　by　58.34%　and　88.16%　compared　to　C40　ordinary　concrete.　The　results　also　show　that　the　density,　longitudinal　wave　velocity　and　porosity　remain　stable　as　soaking　time　increases.　During　the　soaking　process,　the　proportion　of　gel　pores　and　transition　pores　decreases,　while　the　proportion　of　capillary　pores　and　air　pores　increases.　The　UCS　of　geopolymer　pavement　base　material　remains　above　40　MPa　after　soaking　for　90　days,　showing　excellent　water　stability.　The　geopolymer　pavement　base　material　has　the　potential　application　prospect　in　road　engineering　and　emission　reduction,　which　provides　a　feasible　and　cost-effective　method　for　the　utilization　of　waste　sludge.