The utility model relates to a flood control bag for a room door, aiming at providing a flood control bag which is used for the room door and is capable of preventing a body from leaking water, locating at the bottom, sealing at the sides and preventing water seepage of the two sides and the bottom of the body. The flood control bag comprises a bag body made of a soft waterproof material; a bag mouth is formed in the bag body; the bag body is internally filled with granular water absorbing materials; at least one strip-shaped permeable window which is vertical to the horizontal plane is arranged at the front end surface of the bag body; the permeable window is provided with mesh fabric. The flood control bag is made of the waterproof material, and the permeable window is arranged at the front (external upstream face) of the flood control bag, so that the water is enabled to rapidly enter the bag body along with the rising of water level no matter the oncoming force of flood is fast or slow; the bag body is expanded after the water absorbing material is wetted. Secondly, the front end of the bag body is provided with a convex shoulder, and the convex shoulder is arranged outside a door stop; a T-shaped structure formed by the convex shoulder is just closely located with the door stop of the room door no matter how much the external water level difference and the pressure are.