Abstract: Circulating fluidized bed coal combustion fly ash (CFBCF) and ground slag (GCFBCS) were admixed and the properties of the admixture were analyzed. The equal mass replacement of fly ash by admixture and its effects on workability and the strength of the concrete were also studied. The experimental results show that the soundness of admixture is qualified, the index of activity of admixture increases first and then decreases with increase of the FBCF ratio, on the other hand, water demand ratio increases gradually. The maximum index of activity is 84.23% with the 40% FBCF ratio, the water demand ratio meet requirement of FA Ⅱ when the ratio is less than 50%. The workability and strength of concrete made of water reducer which ratio of water reducing agent and slump retaining agent is 1:0.8 and admixture which FBCF ratio is 40% is better than fly ash concrete. Compared with C30 concrete, the admixture contribution to strength especially early age strength is greater for C60 concrete.