In　this　paper,　several　urea–formaldehyde/epoxy　microcapsules　with　different　particle　sizes　were　synthesized　by　in-situ　polymerization.　The　chemical　structure　and　compressive　rupture　load　of　microcapsule　were　characterized.　The　effect　of　microcapsule　dosage,　particle　size　and　preload　pressure　on　compressive　strength　of　cementitious　materials　was　studied.　The　result　shows:　when　the　particle　size　of　microcapsule　is　2　mm~2.5　mm,　the　rupture　load　of　microcapsule　is　highest,　more　than　3N;　When　the　microcapsule　dosage　is　less　than　2.5%,　the　strength　loss　of　the　matrix　is　relatively　small;　With　the　increase　of　the　particle　size　of　the　capsule,　the　strength　of　the　matrix　decrease　greatly;　When　the　dosage　of　microcapsule　is　2.5%,　the　particle　size　is　1.5　mm　and　the　preload　pressure　is　30%~45%fmax,　the　compressive　strength　of　the　self-healing　specimen　is　8%　higher　than　that　of　the　non-preloaded　specimens,　which　shows　a　certain　self-healing　performance.　©　2018　Trans　Tech　Publications,　Switzerland.