Admixtures are widely used in commercial concrete now. Admixtures can improve the workability and homogeneity of concrete, improve the compactness of concrete, reduce water-binder ratio and improve strength. In the mix ratio design, one must fully understand the performance of admixture and water reduction rate, the amount of admixture to choose matters. Admixtures should not be too low, too low content of concrete caused by poor liquidity, poor slump protection, the construction process is not easy to vibrate compaction, easy to appear cavity, honeycomb and pitted surface. But the amount of admixtures should not be too high, too high content will cause concrete segregation, bleeding phenomenon, stratification seriously destroy the homogeneity of concrete, resulting in poor concrete stability, even a long time delay phenomenon. Therefore, in the concrete mix design, according to the concrete workability requirements, select the appropriate amount of admixtures to obtain suitable workability and good uniformity of concrete.