This work is mainly to study the mixing efficiency of the stagger Koch fractal baffles micromixers. They are regularly arranged at the top and bottom of the T-micromixer. The mixing efficiency of stagger secondary Koch fractal baffle (SKFB) micromixer and stagger primary Koch fractal baffle (PKFB) is compared at four kinds of Reynolds (Res). As the angle of the baffles changes, it contributes to enhance the chaotic convection of the micromixer. Especially at angle = 30 degrees, distance (D) = 0.1 mm, the vortex caused by the Koch fractal baffle structure is more obvious at Re = 100, the mixing efficiency of micromixer is more than 95% at Re = 0.05 and Re = 100. On the other hand, the deflection phenomenon caused by SKFB leads to an increasing in the contact area of two fluids which enhances the chaos convection. The concentration curve along the microchannel is studied in this paper, and the concentration curve varies from 0 to 1 mol/L It shows that the flow direction of the fluids in the microchannel changes very obviously which further proof the deflection phenomenon of fluids. The main research is that the Koch fractal curve changes the geometry of obstacles in the microchannel, which induces secondary or reverse flow, and improves chaotic convection and diffusion intensity. This is an essential element for micromixer mixing. (C) 2019 Elsevier Ltd. All rights reserved.