The　mechanical　performance　of　calcium　sulfoaluminate　cement　(CSA)　in　hydrochloric　and　sulfuric　acids　was　studied　and　the　resistance　mechanism　was　investigated.　The　flexural　strength　of　CSA　mortar　in　water　and　acids　was　measured　respectively　and　the　resistance　index　was　calculated.　X-ray　diffraction　(XRD),　thermogravimetric　analysis　(TGA),　electronic　computed　tomography　(CT)　scan,　and　scanning　electron　microscopy　(SEM)　were　used　to　analyze　the　mineral　composition　and　microstructure.　It　is　found　that　compared　with　ordinary　Portland　cement　(OPC),　CSA　shows　better　resistance　to　both　hydrochloric　and　sulfuric　acids,　with　higher　residual　flexural　strength　and　resistance　index　values.　Compared　with　the　portlandite　and　calcium　silicate　hydrate　(the　main　hydration　production　of　OPC),　the　ettringite　(the　main　hydration　production　of　CSA)　is　harder　to　react　with　acids,　which　is　responsible　for　the　better　performance　of　CSA　in　acids.　The　deterioration　of　CSA　in　hydrochloric　acid　is　attributed　to　the　dissolution　of　ettringite　due　to　the　hydrogen　ions,　while　both　hydrogen　ions　and　sulfate　cause　the　deterioration　in　sulfuric　acid.　©　2021　Bulletin　of　the　Chinese　Ceramic　Society　Press.　All　Rights　Reserved.