Main antifloating problems of the twostorey underground parking garage of Yitian village in Shenzhen are presented. Three antifloating methods, i.e., antifloating by anchor bolts, antifloating by punching piles and antifloating by water drainage, are compared and the water drainage method is adopted for the project. The mentioned method uses the theory of “the hydrodynamic pressure being larger than the hydrostatic pressure”, and it can reduce the floating of the structure by controlling the hydrodynamic pressure under the floor. The method used has achieved good effects in the project.