In this work, the mixing efficiency of a rotor-stator spinning disc extractor (RSSDE) is presented. The micromixing efficiency of RSSDE is studied, with the iodide-iodate reaction as working system. The influence of the various operating conditions (e.g. rotational speed, liquid viscosity, volume flow rate, concentration of acid and rotor-stator distance) on micromixing efficiency (characterized by segregation index X-S) is investigated. It is found that the X-S decreases with the rise of rotational speed, the reduction of rotor-stator distance and the concentration of acid and liquid viscosity. Based on the incorporation model, the estimated micromixing times are in the range of 10(-5)-10(-4) s, which is less than that of other tank mixing and rotating devices. In addition, the residence time of liquid in the rotor-stator cavity is researched to describe the effect of independent variables, like rotational speed, volumetric flow rate, rotor-stator distance, and liquid viscosity, with the help of electrical conductance technique. Besides, the corresponding correlation is also established to predict the residence time. The calculation result shows good coincidence with the experimental data, with a deviation within 20%.