A parallel-competing chemical test reaction was performed in a Higee liquid/liquid system to evaluate the micromixing efficiency. According to the experimental results, it indicated that increasing rotational speed and liquid flow rate could intensify micromixing effectively. The micromixing efficiency in a Higee system was shown to be higher than other reported types of mixing devices, and the centrifugal force was also effective in enhancing micromixing when the liquid viscosity increased. An empirical correlation was then obtained, implying that the characteristic mixing time was proportional to the rotational speed to the power of -0.64. To investigate the relation between micromixing and mass transfer, an experiment of deoxygenation was performed. It is found that mass transfer resistance decreased as the micromixing efficiency increased.