Due　to　the　different　hydration　mechanism　of　cement　mixed　with　alkaline　and　alkali-free　accelerators,　there　are　obvious　differences　in　application　performance.　In　this　paper,　the　application　performance　and　early　hydration　process　of　two　accelerators　were　comprehensively　analyzed　through　the　test　of　macroscopic　properties　such　as　setting　time　and　compressive　strength　of　mortar,　and　the　microscopic　methods　such　as　hydration　heat　analysis,　XRD　quantitative　analysis,　thermogravimetric　analysis　and　scanning　electron　microscope　observation.　The　results　show　that　the　[Al　(OH)4]　-　accelerates　the　consumption　rate　of　gypsum　in　cement　and　a　large　amount　of　ettringite　(AFt)　are　generated　in　the　initial　hydration　stage　after　the　alkaline　accolerator　is　added　to　the　cement.　At　the　same　time,　the　alkaline　accolerator　also　promotes　the　hydration　of　C3S　minerals,　shortens　the　setting　time　of　cement　paste　and　improves　the　early　compressive　strength　of　mortar.　However,　the　accelerated　consumption　of　gypsum　also　makes　the　hydration　products　such　as　monosulfurtype　hydrated　calcium　sulfoaluminate　(AFm)　and　hydrated　calcium　aluminate　(C-A-H)　form　in　advance,　which　negatively　affects　the　long-term　compressive　strength　development　of　cement-based　materials.　While　the　alkali-free　accelerator　is　added　to　the　cement,　the　[Al(OH)4]　-　and　SO24-　form　a　large　amount　of　AFt　in　the　liquid　phase,　which　promotes　the　hydration　of　C3A　and　C3S　minerals,　and　affects　the　crystallization　and　precipitation　of　Ca(OH)2(CH).　It　is　worth　noting　that　SO24-　from　the　alkali-free　accolerator　not　only　promotes　the　process　of　C3A　to　generate　AFt,　but　also　delays　the　consumption　of　gypsum　in　cement　and　the　formation　of　hydration　products　such　as　AFm　and　C-A-H.　Therefore,　the　28　d　compressive　strength　is　not　negatively　affected　in　addition　to　the　obvious　improvement　of　the　early　compressive　strength.　©　2022　The　Author(s).