Many problems of gasifiers, such as the heat value produced by gas is very low and much tar remains in the gas during the process of operation. Focusing on these, a new internal combustion type heating gasifier was designed according to the principle of biomass gasification. This type is superior to the fixed bed gasifier and the fluidized bed gasifier, which already existed. Similar to the down draft fixed bed gasifier, the tar in the gas content is very low. By designing an internal heating system taking gas as the fuel, the quantity of the air entering the gasifier was reduced, and the quality of the gas was improved. This gasifier combines biomass gasification and catalytic cracking together so that there is no need to provide the heat source again for catalytic cracking. Inner rotary mechanism, snake pipe internal combustion heat exchanger device, atomization humidification equipment and so on make the gasifier perform well.