Abstract: By means of chemical coupling method,micromixing of non- Newtonian fluids in a semicontinuous stirred vessel was investigated and the effect of several factors on segre-gation index,a parameter for characterizing micromixing quality,was studied.It is found that the mixing becomes poor with an increase in viscosity to different extent depending on viscos-ity ranges and improving mixing by intensifying agitation is available only within a range of rotational speed.It seems to be a critical operating speed related to fluid pseudoplastic prop-erty.Besides,micromixing performance can be promoted by a reasonable combination of different types of impeller.