The　particle　shape　index　of　standard　sand，river　sand，and　three　types　of　manufactured　sand　was　measured　and　analyzed　using　digital　image　processing（DIP）technology.　And　the　influence　of　manufactured　sand　particle　shape　on　the　corrosion　resistance　of　mortar　under　the　coupling　effect　of　Cl-　and　CO2　was　studied.　The　results　indicate　that　the　particle　shape　index　of　manufactured　sand　is　lower　than　that　of　river　sand，and　is　significantly　affected　by　the　content　of　flake　particles.　Under　the　coupling　corrosion　of　Cl-　and　CO2，the　pH　value　at　the　endpoint　of　the　convective　zone　is　12.0-12.5.　As　the　particle　shape　index　of　fine　aggregate　decreases，the　content　of　free　Cl-　and　the　apparent　Cl-　diffusion　coefficient　in　the　mortar　first　decrease　and　then　increase，showing　a　positive　correlation　with　the　proportion　of　risk　pores　with　pore　diameter　larger　than　50　nm，and　are　influenced　by　the　duration　of　CO2　erosion　within　a　single　cycle.　The　decrease　of　particle　shape　index　of　fine　aggregate　enhances　the　tortuous　effect　of　fine　aggregate　and　improves　the　retarding　effect　of　fine　aggregates　on　external　corrosion.　It　is　recommended　that　the　appropriate　particle　shape　index　for　manufactured　sand　be　set　at　around　0.8.　©　2025　Tongji　University.　All　rights　reserved.