The invention relates to a plasma submerged heating system and a tubular plasma gun. The plasma submerged heating system is characterized in that the plasma gun is used for directly spraying high-temperature plasma gas into metal or inorganic non-metal melt in a jet or bubbling mode, and the metal or inorganic nonmetal raw material layer floats on the metal, and is continuously melted and enters the melt; high-temperature gas which escapes from the melt enters the raw material layer floating on the melt, and is discharged after heat exchange; according to the structure of the gun, a certain amount of plasma sprayers are successively arrayed in a cavity of a hollow tube, nozzles of the plasma sprayers are matched with air spraying holes arrayed in the wall of the hollow tube, and cooling fluid is fed into the cavity of the hollow tub and is used for cooling and protecting the hollow tube and the plasma sprayers; and an air supply tube is arranged in the cavity of the hollow tube, and provides working gas for the various plasma sprayers. The plasma gun is soaked in the metal or inorganic non-metal melt; and the tubular plasma gun is soaked in the melt during working.