The invention discloses an apparatus for spraying and processing interior surface of a gas tank, which comprises a track, a carriage cooperated with the outer wall of the gas tank is arranged on the track in a slidable mode, a driving roller and a driven roller with equal height along the track direction are arranged on the sidewall of the groove of the carriage, a non-powered backing roll is arranged at the center of the bottom of the groove, a bracing frame is arranged at the right side of the track, a hollow driven rotating shaft is arranged on the bracing frame, a disk device shell is arranged at the end part of the driven rotating shaft, a liquid spraying pipe is distributed at interval along the radial direction at the peripheral part of the shell, an atomizing nozzle is provided at the end part of the liquid spraying pipe, and an liquid inlet pipe communicated to the shell is arranged at the center of the driven rotating shaft. The design of a structure of the apparatus is novel, the gas tank is arranged on the guide rail for horizontal moving and feeding, simultaneously, the gas tank is rotated with uniform speed, in addition, the shell is arranged on the driven rotating shaft for rotating, multiple regulation and control are carried out for spraying the inner wall of the gas tank, spraying efficiency and uniformity are increased, completion of one-time spraying can be ensured, and no impurity pollution is generated on the interior surface of the tank after spraying.