The invention relates to the technical field of water pipe detection devices, in particular to a water leakage detection device for an underground water pipe. The water leakage detection device comprises a positioning sleeve, a hydrodynamic ball in the water pipe and card readers in the area where the water pipe is located. The positioning sleeve is internally provided with an electromagnet for attracting the hydrodynamic ball. The hydrodynamic ball comprises an inner shell and an outer shell. The inner shell is provided with a plurality of first through holes. The outer shell is provided witha plurality of second through holes aligned with the first through holes. Sealing films are arranged inside the second through holes for sealing the second through holes. The first through holes areinternally provided with a plurality of barb protrusions for puncturing the sealing films. A magnetic part is fixedly arranged in the hydrodynamic ball. An RFID label is arranged inside the hydrodynamic ball. Leak-proof fluid fills the hydrodynamic ball. The number of the card readers is at least three, and the card readers are used to obtain the positioning of the hydrodynamic ball through reading of the RFID label signal strength. The scheme can be used to detect whether the groundwater pipe leaks or not, and the leaking place can be accurately found for temporary leak seal.