The invention discloses a water leakage prevention device for a floor mopping machine. The device comprises a ground brush body, the ground brush body is a of a box-shaped structure, two rolling brushes are arranged inside a rolling brush body, arc flow guiding plates are arranged around the rolling brushes, an arc flow guiding plate between the two rolling brushes and the bottom face of the ground brush body to form a sewage box, an opening of the sewage box faces upwards, the sewage box is detachable, an axial rotating shaft and two cover plates are arranged at the opening of the sewage box,the cover plates are connected in a pivoted mode by means of hinge connection, and can rotate around the rotating shaft, an elastic piece is arranged among the cover plates and the rotating shaft, after the cover plate covers the sewage box, the height of the ends, connected with the rotating shaft, of the cover plates is lower than the other ends of the cover plates, an opening is formed in theposition, close to the sewage box, of the arc flow guiding plate, scraping teeth are arranged at the opening, and the scraping teeth are inclined downwards. The sewage box for recycling sewage and dirt obtained after floor mopping is arranged, the cover plates are arranged, and the problem that sewage leakage is caused when the floor mopping machine vibrates in the working process can be effectively avoided.