Calcium　alginate　microcapsules　loaded　with　epoxy　were　successfully　prepared　by　a　piercing-solidifying　method,　and　applied　to　self-healing　cementitious　materials.　The　structure,　mechanical　strength　and　water　swelling　properties　of　the　microcapsules　were　characterized,　and　the　healing　mechanism　of　microcapsules　was　monitored　by　X-ray　computed　tomography　and　SEM/EDS.　The　results　showed　that　the　microcapsules　were　three-dimensional　network　structures;　the　strength　of　the　microcapsule　with　particle　size　of　0.7-2　mm　was　independent　of　the　particle　size;　and　the　content　of　calcium　alginate　in　microcapsule　determined　the　strength,　water　absorption　and　swelling　ratio　of　the　microcapsule.　The　healing　mechanism　of　calcium　alginate/epoxy　microcapsules　in　cement　matrix　was　observed　that　when　cracks　formed,　the　microcapsules　were　broken　to　release　the　epoxy　resin,　bonding　the　cracks;　when　water　penetrated　into　the　cracks,　the　microcapsules　absorbed　and　swelled,　blocking　the　cracks　and　even　promoted　the　cement　particles　continue　to　hydration,　healing　cracks.　©　2018,　Materials　Review　Magazine.　All　right　reserved.