The invention discloses a sunken construction method of a battery swap station, and relates to the technical field of battery swap station construction. The sunken construction method comprises the steps that 1, a foundation and a water collecting well are dug downwards; 2, the bottom surface and the side wall of the foundation are flattened; 3, the surface layer of the foundation is solidified, waterproof treatment is conducted, and base bearing piles are reinforced; 4, horizontal auxiliary materials are laid, specifically, the horizontal auxiliary materials are laid at the bottom of the solidified foundation or on a reinforcing seat, the levelness of the horizontal auxiliary materials is measured through an instrument, and the laid horizontal auxiliary materials are leveled and fixed; 5,a lubricant is coated on the surface of a track of the horizontal auxiliary materials; and 6, the battery swap station is mounted, specifically, namely the battery swap station is mounted on the horizontal auxiliary materials, the mounting position of the battery swap station is finely adjusted on the horizontal auxiliary materials, and the battery swap station is precisely mounted. By means of small-scale excavation, it can be guaranteed that the battery swap station is mounted in the narrow foundation, the construction quality can be guaranteed, the cost can also be saved, and meanwhile thewater collecting well further has the fire-fighting function of the battery swap station.