Abstract: To meet the requirements of compactness and high mass transfer efficiency for the gas absorber of closed cycle diesel engine （CCDE）, and address the issue of unclear correlation between the microflow characteristics of the absorber and rotating speed as well as liquid flow rate, visualization experiments and computational fluid dynamics （CFD） simulations were carried out in combination. The results show that the liquid phase in the cavity region is mainly composed of liquid line flow and droplet flow, extending along the involute, and the velocity of droplets remains stable after they fly off the rotating disc, with the average velocity being only positively correlated with the rotating speed. A CFD model of the disc region established based on the volume of fluid （VOF） model and k-ω turbulence model has good reliability, and the error between the calculated and experimental values of droplet velocity is ≤7%. The flow patterns in the disc region include three forms, i.e., liquid film, liquid line and droplet. With the increase of rotating speed/liquid flow rate, the upper surface presents a transition of “pure liquid film flow → liquid film−droplet flow → liquid film−liquid line−droplet flow”, and the transition critical conditions can be defined by quantitative relational expressions. An increase in rotating speed reduces the liquid holdup and wetted area but increases the specific surface area of the liquid, while an increase in liquid flow rate only significantly increases the liquid holdup and wetted area. Among them, the liquid phase dispersion is optimal under the “liquid film−liquid line−droplet” flow pattern, which is the key state for enhancing the performance of the gas absorber.