As a result of the increasing impact of cement kiln flue dust on human health and the environment. In this study, cement kiln flue dust was used as an alkaline activator for mixed cement made from ordinary Portland cement (OPC) and metakaolin (MK). In the first part of the research, the mechanical properties of mixed cement pastes containing different proportions of metakaolin were studied to obtain the best mixture of metakaolin and cement. Various ratios of metakaolin were substituted for MK (5, 10, 15, 20, and 25 %) to obtain the best ratio between OPC and MK. Incorporation of cement kiln flue dust in 15MK mix by different weight ratios (2, 4, 6, 8, and 10%) as a partial substitution ratio from OPC ratio was investigated to improve the pozzolanic activity of MK especially at early ages of hydration. To realization investigate the effect of cement kiln flue dust on MK cement binder, classical tests of setting times and strength at various ages. The results were analyzed by using advanced devices. The results indicated that the MK has a positive effect on the physicomechanical properties of cement. The 15MK mix exhibited the best results regarding the physicochemical and mechanical properties of hardened cement paste, especially at later ages of hydration. The compressive strength of the 15MK mix increased about 23.53% compared with the neat OPC at 28 days of hydration. Based on the physicochemical and mechanical measurement, incorporation of 6% CKFD with 15 % MK in blended cement paste improved the physico- mechanical properties of the hardened cement.