The invention discloses a bottom door device of a railway freight car. The bottom door device comprises a gravity action type bottom door plate, and is characterized in that a rigid frame is fixedly mounted on the periphery of the lower edge of a funnel mouth of the railway freight car, a groove is arranged on the rigid frame, an opening of the groove is downward, a sealing strip is mounted in the groove, the sealing strip comprises a head part and a body part, the head part is embedded into the groove, and the body part extends out of the groove. The bottom door device disclosed by the invention can not only overcome the defects of poor sealing performance of a gravity action type bottom door and large impact during opening and closing of the bottom door, but also overcome the defects of poor bearing performance of the bottom door and incapability of realizing mechanical self-locking of an existing drawing plate type bottom door, has good transportation sealing property and reliability, and can meet the requirements of sealing in transportation of powdered and bulk cargoes, effectively reduce the leakage quantity of the cargoes and realize broad application prospects.