Gypsum　is　an　indispensable　component　of　ordinary　Portland　cement.　The　main　function　of　gypsum　is　to　regulate　the　setting　time　of　cement.　Gypsum　has　a　great　influence　on　water　consumption　of　standard　consistence　and　strength　simultaneously.　In　this　article　three　cementitious　systems　are　prepared　by　three　main　mixed　materials:　limestone,　fly　ash　and　slag.　The　effect　of　gypsum　content　and　the　relation　between　gypsum　quantity　and　the　fluidity　of　cement　with　Marsh　cone　method　are　studied.　Experimental　results　show　that　when　the　gypsum　was　added　in　the　three　kinds　of　cementitious　system,　water　consumption　of　standard　consistence　decreased　obviously,　and　with　the　quantity　of　gypsum　increased,　water　demand　for　normal　consistency　reduced　first,　up　to　a　certain　extent　tended　smoothly.　With　the　increase　of　gypsum　quantity,　initial　and　final　setting　time　had　different　degrees　of　extension.　While　a　saturation　quantity　is　achieved,　setting　time　will　keep　steady.　The　flexural　strength　and　the　compressive　strength　increased　gradually　and　tended　to　be　stable　with　the　increase　of　gypsum　quantity.　When　gypsum　content　exceeded　a　certain　range,　compressive　and　flexural　strength　decreased　gradually.　But　gypsum　content　and　the　mobility　of　systems　had　little　relativity　with　Marsh　cone　method.