In　order　to　consider　the　influence　of　the　initial　defect　shape　of　materials,　it　was　assumed　to　be　a　three-dimensional　semi-ellipse.　Based　on　the　theory　of　fracture　mechanics,　the　expansion　process　of　the　rust　expansion　cracking　can　be　divided　as　two　critical　stages:　the　initial　cracking　stage　and　the　complete　cracking　stage,　which　were　both　analyzed.　A　prediction　model　of　rust　expansion　force　and　cracking　time　was　established　when　concrete　cover　cracks.　The　proposed　model　was　verified　using　the　pre-existing　indoor　corrosion　test　and　field　test　data,　and　the　results　showed　that　the　prediction　model　is　reasonable.　On　this　basis,　parameter　sensitivity　analyses,　such　as　the　length　of　the　initial　defect,　the　concrete　cover　thickness,　the　reinforcing　bar　radius,　the　relative　cover　thickness　were　analyzed,　the　results　showed　that　the　service　performance　of　RC　structures　can　be　improved　by　increasing　the　concrete　cover　thickness　and　the　relative　cover　thickness.　©　2020,　Editorial　Department　of　Journal　of　Northeastern　University.　All　right　reserved.