This　paper　presents　the　effects　of　mineral　admixtures　and　the　water　to　binder　ratio　(W/B)　on　the　tensile　and　compressive　strength　and　micro　pore　structure　of　hardened　cement　pastes.　The　test　results　show　that:　with　the　water　to　binder　ratio　increasing,　the　tensile　and　compressive　strength　of　cement　paste　with　different　mineral　admixtures　will　decrease,　air　content　and　mean　pore　diameter　will　decrease　and　the　cement　paste　with　the　ground　blast　furnace　slag　is　the　lowest.　The　artificial　neural　network　based　on　its　nonlinear　mapping　function　can　fit　the　relationship　between　strength　and　pore　structure　more　accurate　than　an　empirical　formula.