An　artificial　alternative　material　for　natural　sand　in　construction　is　of　significance　for　the　civil　engineering.　In　the　present　study,　the　effects　of　artificial　geopolymer　sand　(AGS)　as　an　alternative　to　natural　sand　(NS)　on　pore　structure　and　mechanical　property　of　cement　mortar　were　studied.　First,　six　groups　of　cement　mortar　specimens　were　prepared　with　the　different　replacement　ratios　(0.0%,　20.0%,　40.0%,　60.0%,　80.0%　and　100.0%).　Then,　a　series　of　nuclear　magnetic　resonance　(NMR)　tests　were　performed　to　study　the　effects　of　replacement　ratio　on　the　density,　total　porosity　and　percentage　of　different　size　pores.　Finally,　the　ultrasonic　wave　and　uniaxial　compressive　tests　were　performed　to　study　the　effects　of　replacement　ratio　on　the　P-wave　velocity,　strength　and　elastic　modulus.　The　results　show　that　the　density　and　P-wave　velocity　decrease　linearly　as　the　replacement　ratio　increases.　The　total　porosity　increases　slowly　at　first　and　then　increases　rapidly　as　the　replacement　ratio　in-creases.　The　increase　in　replacement　ratio　induces　the　more　significant　increase　in　the　smaller　pores　compared　with　the　larger　pores.　The　strength　and　elastic　modulus　firstly　increase　and　then　decrease　as　the　replacement　ratio　increases.　The　strength　and　elastic　modulus　decreased　by　11.0%　and　5.4%　when　replacement　ratio　reaches　100%.