In　new　dry　way　predecompostion　cement　production,　after　preheating,　raw　meal　comes　into　a　calciner,　and　occurs　decomposition　reaction,　then　freshly　generated　CaO　comes　into　a　solid-phase　reaction　process　in　the　kiln　The　three　stages　are　closely　related　and　interacted　on　each　other.　The　formation　rate　of　clinker　mineral　phases　is　closely　related　to　the　activity　of　CaO　generated　by　the　decomposition　reaction,　and　high　activity　CaO　is　helpful　to　accelerate　the　formation　of　mineral　phases　and　decrease　the　corresponding　calcining　temperature.　However,　there　are　large　differences　in　activity　values　of　CaO　gennerated　under　various　calcination　conditions,　and　differet　activated　CaO　has　a　different　effect　on　the　solid-phase　reaction　and　dynamics　of　clinker　formation.　In　this　paper,　in　order　to　study　the　influence　of　different　decomposition　temperatures　on　the　activity　of　generated　CaO　during　solid-phase　reaction,　the　content　of　free　CaO　after　the　reactions　between　the　decomposition　products　of　limestone　under　different　calcination　temperatures　and　SiO2　was　determined　by　chemical　analysis,　and　the　content　of　CaO　involved　in　the　reaction　was　calculated.　The　results　show　that　at　the　limestone　decomposition　temperature　of　900　degrees　C,　the　content　of　CaO　participated　in　the　reaction　in　clinker　was　increased,　CaO　activity　was　increased,　these　all　were　beneficial　to　the　chemical　reaction.　Excessive　decomposition　temperature　can　decrease　the　reaction　activity　of　CaO,　so　an　appropriate　decomposition　temperature　is　necessary　to　make　the　majority　decomposition　of　raw　meal　completed　in　the　calciner,　and　ensure　that　generated　CaO　maintained　a　better　activity　state　into　the　kiln　to　participate　in　the　solid　state　reaction.