In　order　to　detect　the　influence　of　age　on　the　experiment　that　use　scanning　electron　microscopy　(SEM)　to　determinate　the　original　water-cement　ratio　(w/c)　of　hardened　concrete,　a　series　of　concrete　mixes　are　tested.　Experimental　results　show　that　early　ages　do　have　an　effect　on　the　water-cement　ratio　of　hardened　concrete　that　determined　from　scanning　electron　microscopy,　this　effect　will　decrease　while　age　increases.　The　relationship　between　capillary　porosity,　w/c　and　age　is　analyzed　and　a　calculation　equation　is　given.　©　(2014)　Trans　Tech　Publications,　Switzerland.