Effect　of　iron　ore　tailings　as　fine　aggregate　on　pore　structure　of　mortars　has　been　studied　in　this　paper.　The　purpose　is　to　investigate,　as　fine　aggregate,　comparing　to　natural　sand,　whether　the　iron　ore　tailings　can　improve　the　pore　structures　of　mortars　or　not.　Pore　structure　parameters　were　measured　with　the　instrument　of　MIP　and　calculated　with　corollary　software.　The　pore　structure　parameters　from　four　kinds　of　mortars　with　different　fine　aggregates　are　compared　with　each　other.　This　paper　will　provide　more　data　about　the　use　of　this　artificial　aggregate,　which　may　increase　the　feasibility　of　the　use　of　this　by-product　in　the　mortar　or　cement　concrete　industry.