Visual observation technology and nonlinear fitting method were adopted to analyze the fluid behavior characteristics in the cavity of the rotating disk reactor. Water, glycerol and sodium dodecyl benzene sulfonate solution were selected as working fluids. A high-speed camera and Image J image processing software were used to investigate the flow patterns and breakup modes of fluid in the cavity. The critical condition equation for flow pattern transition was fitted, and the influence laws of operating parameters on the characteristic droplet diameter and droplet distribution uniformity index were explored. Results show that the typical flow patterns include ligament flow, ligament-droplet flow, and droplet flow. Meanwhile, the breakup mechanisms consist of film-to-droplet and film-to-ligament-to-droplet transitions. The cumulative droplet volume follow the Rosin-Rammler (R-R) distribution, with characteristic droplet diameters ranging from 1 to 4 mm, and the droplet distribution uniformity index between 2 and 8. Rotor speed and fluid viscosity significantly influence on the fluid behavior characteristics in the cavity zone. The findings contribute to a deeper understanding of the internal fluid behavior characteristics of supergravity devices and can provide basic data and theoretical references for constructing mass transfer models.