Abstract: A 3-d regional floating dust event occurs in Guangdong-Hong Kong-Macao Greater Bay Area (GBA) from 13 April to 15 April in 2025. Multi-source observations, including meteorological and air quality measurements, meteorological gradient tower data, lidar, wind profile, FY-4B meteorological satellite products, and sounding data, are combined with synoptic analysis and HYSPLIT (Hybrid Single-particle Lagrangian Integrated Trajectory) model simulations to investigate causes for the formation and persistence of this event. Results show that during this floating dust event, visibility across GBA drops sharply from 25 km to below 10 km and remained in the range of 7-10 km for an extended period. Meanwhile, PM₁₀ concentration surges by 10-20 times within 24 h, resulting in PM₁₀ pollution recorded in all GBA cities. The hourly peak PM₁₀ concentration in Guangzhou reaches 448 μg·m^-3. HYSPLIT backward trajectory simulation indicates that the long-range transport of dust from the northern China is the direct cause of the floating dust event in GBA. The establishment of a low-level jet and the enhancement of subsidence provides dynamic conditions for the continuous transport of upstream dust into the region and its downward diffusion. Vertical aerosol variations further corroborate that over southern GBA (e.g., Shenzhen) between approximately 200 m and 1.2 km, subsequently accumulating mainly near the surface and causing a rapid rise in ground-level PM₁₀ concentrations. The East Asian trough, Mongolia cyclone, and cold front, which guide the cold air southward rapidly, act as the key dynamic drivers of this long-range dust transport. The prolonged maintenance of the floating dust results from the combined influence of multiple factors. During the persistence stage, horizontal wind speeds at 520-m height in the boundary layer are generally below 8 m·s^-1, and the atmosphere conditions remained stable and dry for approximately 36 h, which respectively suppressed horizontal and vertical diffusion. Additionally, sea-land breeze convergence further enhances the accumulation of particulate matter. Finally, the low-level easterly to southeasterly flow promotes the recirculation transport of marine-sourced floating dust aerosols, thereby delaying the dissipation of this floating dust event in GBA.