The invention provides a fixed bed pressurized gasification system and relates to the technical field of gasification processes, aiming at solving the problems that the content of methane in produced coal gas is high and influences on a production capacity of the system are relatively great. The fixed bed pressurized gasification system comprises a gasification reactor, a methane conversion device, a coal gas waste boiler, a washing saturation tower and an ash water treatment system, wherein a gas inlet of the methane conversion device is communicated with a gas outlet of the gasification reactor; a gasification agent inlet is arranged in the top of the methane conversion device; a gasification agent which enters the methane conversion device from the gasification agent inlet comprises oxygen; the coal gas waste boiler is communicated with a gas outlet of the methane conversion device; the washing saturation tower is communicated with the coal gas waste boiler; the ash water treatment system is communicated with the gasification reactor, the coal gas waste boiler and the washing saturation tower respectively. By adopting the fixed bed pressurized gasification system provided by the invention, the disadvantages that the content of methane in the produced coal gas is high, the coal gas carries organic matters including coke tar and the like can be effectively overcome.