The　high　geothermal　environment　causes　a　temperature　gradient　inside　shotcrete,　which　affects　the　development　of　its　mechanical　strength.　This　research　investigated　the　strength　evolution　of　shotcrete　in　simulated　high　geothermal　environment　by　applying　a　unidirectional　heat　source.　The　influence　of　temperature　gradient　on　the　pore　structure,　morphology,　phase　composition,　and　hydration　degree　of　shotcrete　was　also　studied.　It　was　found　that　the　early　strength　of　shotcrete　was　improved　but　that　the　later　strength　was　reduced　in　the　high　geothermal　environment.　It　was　attributed　to　the　increase　in　harmful　porosity　and　total　porosity　of　the　concrete　caused　by　the　high-temperature　curing.　Cracks　and　pores　can　be　observed　in　the　microstructure　near　the　heat　source　region.　Besides,　the　ettringite　content　in　shotcrete　was　lower　than　that　under　standard　curing　environment　and　presented　gradient　distribution　in　the　direction　of　the　temperature　gradient.　©　Wroclaw　University　of　Science　and　Technology　2024.