Grinding　aids　(GAs)　are　an　important　addtive　in　the　cement　production　process.　However,　the　relationship　between　the　molecular　structure　of　GAs　and　its　grinding　efficiency　has　not　been　clearly　revealed.　In　this　study,　the　influence　of　GAs　with　different　structures,　including　glycols　and　alkanolamines,　on　the　grinding　efficiency　of　pure　clinker　was　systematically　investigated.　The　working　mechanism　from　their　adsorption　and　dispersion　configurations　on　tricalcium　silicate　(C3S)　surface　was　investigated　by　first-principles　method.　As　the　structural　parameters　of　GAs,　number　of　polar　groups　is　found　to　affect　the　grinding　efficiency　of　cement　clinker.　The　grinding　performance　of　alkanolamines　is　better　than　that　of　glycols　at　the　same　dosage,　when　the　number　of　hydroxyl　groups　is　the　same.　The　tertiary　alkanolamines　are　adsorbed　through　the　double-ended　hydroxyl　group　to　form　larger　molecular　projection　areas　than　the　glycols　with　single-ended　hydroxyl　group,　thus　resulting　in　higher　dispersion　efficiency.　Further,　with　the　growth　of　the　number　of　methyl　groups　in　the　molecular　structure　of　the　tertiary　alkanolamines,　the　thickness　of　the　adsorbed　molecular　layer　grows　from　9.25　&　Aring;　to　9.87　&　Aring;,　and　the　ability　to　shield　the　electrostatic　forces　between　cement　particles　is　enhanced　and　result　in　a　better　grinding　aid　performance.