Abstract: In view of the problem of anti floating of high groundwater level and ultra deep basement structure in the Pearl River Delta, the traditional passive anti floating methods, such as uplift piles and anti floating anchors, often lead to high engineering costs and long construction period. Relying on the Guangzhou municipal group intelligent construction R&D headquarters project, this paper puts forward and practices a "drainage based" active anti floating technology - Drainage decompression method. By constructing an organized drainage system consisting of a sand free concrete drainage well, a graded gravel drainage layer, a drainage pipe, a sump and an automatic drainage pump, the technology can effectively reduce the groundwater level, thereby significantly reducing the water pressure acting on the basement floor. The engineering practice shows that under the rainstorm condition, the method successfully reduces the water pressure of the floor from 150 kPa to below 20 kPa, meeting the structural safety requirements. Compared with the traditional uplift pile scheme, the project cost is saved by about 30million yuan, and the economic benefit is remarkable. At the same time, the discharged groundwater is collected and used for garden irrigation, which realizes the recycling of water resources and conforms to the concept of green building and sustainable development. This study provides a new idea and reproducible technical path for the anti floating design of ultra deep basement in high water level area.