The invention discloses a biomass (especially briquette straw) gasification furnace, in particular a fixed bed gasification furnace with an anticorrosion liner which can effectively prevent corrosion of alkali metals on the furnace wall. The gasification furnace comprises a charging device (1), a gas discharge port (2), a furnace body (3), a grate (4), a dust discharge port (5), an air inlet (6) and the like. The raw material is continuously added from the upper part and moves downwards under the action of gravitation to form a stable reduction layer (completely reacts with oxygen in air), and slag is discharged from the bottom; and air enters from the lower part, and gas is discharged from the upper part. The inner diameter of the gasification furnace is 3 m, the height is more than 3 m, and the gasification intensity is at least 100 m<3>/(m<2>h). The carbon conversion rate of the gasification furnace can reach 95%, and the oxygen content of gas can be below 0.6%. The invention has the advantages of high production capacity, long operating cycle and good gas quality, and can be used for combustion or power generation.