The alkylation of isobutane with 2-butene catalyzed by ionic liquid (IL)/solid acid (SA) was studied in this work. To improve the product quality, the rotating packed-bed (RPB) reactor was used to enhance the mass transfer of the alkylation process. Residence time, reaction temperature, the isobutane-to-olefins ratio, and the acid-to-hydrocarbon ratio all markedly affected the quality of allcylates. Under the optimal conditions, the research octane number could reach 99.8, and the amount of trimethylpentanes was 87.1 wt %. Because of the high efficiencies of mass transfer and micromixing, the RPB reactor can greatly improve the reaction efficiency of isobutane alkylation. By observing the droplets in RPB, the relationship between the average droplet diameter and the interfacial area was investigated. The droplet diameter and interfacial area were highly dependent on the physical parameters, such as the acid-to-hydrocarbon ratio, rotational speed, and the interface tension of acid-hydrocarbon. Moreover, a correlation model was proposed to calculate the interfacial area of the RPB reactor. A smaller droplet diameter and larger interfacial area are beneficial to the production of high quality alkylates. RPB is one of the promising industrial reactors for ionic liquid/solid acid alkylation.