A rail bracket securing structure may have a locking base, a sliding block and a locking rack. One end of locking base has a hook portion bended perpendicularly to the locking base, and a receiving space is formed at the other end thereof, and an outer restricting piece is formed at both sides outside the hook portion. The sliding block is U-shaped with two parallel pins and a driving portion, and the sliding block is disposed at the receiving space of the locking base and the pins are protruding at the hook portion. One end of the locking rack has a fixed portion that is used to conjugate with a rail at its outer portion, and the other end has a covering board to cover the receiving space of the locking base, so that the sliding block is restricted between the locking base and the locking rack.