Abstract: Based on the analysis of the traditional kinetics mechanism about mixing and the comparison of the relat ive magnitude of macroscopic and microscopic mixing time, a new kinetics mechanism on mixing in turbulence is presented.The speed of macroscopic mixing is controlled by eddy diffusion, and the speed of microcosmic mixing is controlled by molecular diffusion.The mixing process is dominated by macroscopic mixing.The Euler number can be used as the cont rol parameter that determines the mixing efficiency.The mixing tests are conducted in three reactors of different volumes to verify the practicality of this index.