The invention relates to a water collecting tank anti-floatation device, which comprises a plurality of water collecting tanks, wherein the tail end part of each water collecting tank is connected with a water inlet formed in the front end of a water tank. The water collecting tank anti-floatation device is characterized in that a plurality of water inlet holes B with equal intervals are formed inthe two side edges of the water collecting tanks; water inlet holes A are formed in the front ends of each water collecting tank; a steel plate is also hinged to the front ends of the water collecting tanks; a triangular plate module is arranged at the bottom of a position, near the tail end, of the water collecting tank; an emptying opening is formed in a position, positioned at the front end ofthe triangular plate module, of the bottom of the water collecting tank. The water collecting tank anti-floatation device has the beneficial effects that the structure is compact; the stability is high; the stability of the water collecting tanks can be improved through the arrangement of the triangular plate module; the water collecting tank swinging and noise generation due to low water level of the water collecting tanks cannot be caused; meanwhile, a plurality of water inlets are formed in the front end and two side edges of the water collecting tanks, so that the flowing-in of a great number of suspended matters from the water inlets can be avoided; the clean water quality is improved.