The invention relates to a furnace body structure of a pressurized gasifier. The furnace body structure is provided with a vertical outer barrel. An inner barrel is arranged in the outer barrel. The space between the inner barrel and the outer barrel is filled with boiler water. The inner wall of the inner barrel is provided with a titanium alloy steel plate vapor barrier layer and a refractory insulating brick layer. The refractory insulating brick layer is formed by splicing and laying multiple rectangular lock catch refractory bricks. At least one side among four sides of each rectangular lock catch refractory brick is provided with a cylindrical flange, the other side, symmetric with the cylindrical flange, of the rectangular lock catch refractory brick is provided with a cylindrical groove, and the cylindrical flange is matched with the cylindrical groove. The refractory insulating brick layer is resistant to wear, corrosion and high temperature; the vapor barrier and heat insulating filler layer is resistant to high temperature, acid and alkali and capable of isolating corrosion of corrosive gases on the barrels.