The invention discloses a bio-retention pond capable of continuously processing initial rainwater in a drought period. The bio-retention pond comprises an adjusting area and a water storage area. The adjusting area comprises an adjusting tank, the adjusting tank is connected with a municipal rainwater pipe network, and the adjusting tank is internally provided with a water inlet communicated with the water storage area. The water storage area comprises a reservoir, a floating plate is hinged in the reservoir, and one end of the floating plate is equipped with a floating drum. The floating plate is equipped with a first sealing plate, the reservoir is equipped with a baffle floating block, and the bottom of the reservoir is equipped with a submersible sewage pump connected with a controller. The submersible sewage pump is connected with the bio-retention pond via a pressure water inlet pipe, and the bio-retention pond is provided with an overflow water return pipe connected with the reservoir. The initial rainwater can be individually collected and stored and used in association with the bio-retention pond, so that the high-pollution initial rainwater can be processed concentratedly, continuously and circularly. The bio-retention pond is environment-friendly, and is suitable for wide-range application in construction of sponge cities.