The invention discloses a biomass gasification gas-powder mixed combustor which comprises a coarse storage bin, a fine storage bin, a first feeder, a secondary feeder, a biomass vaporizing chamber and a gas-powder mixed chamber which are respectively provided with a clamping sleeve, a first air pipe line, a secondary air pipe line and a slag removal notch, wherein biomass fuels in two storage bins respectively enter the biomass vaporizing chamber and the gas-powder mixed chamber through a first feeder and a secondary feeder, a jacket of the biomass vaporizing chamber is composed of an inner furnace wall and an outer furnace wall, preheated air enters the biomass vaporizing chamber through the jacket of the biomass vaporizing chamber; the combustion process of the biomass comprises two stages, step 1. air vaporization: converting the biomass into combustible gas, and introducing the combustible gas into the gas-powder mixed chamber to mix; and step 2. according to the biomass semicoke content, changing the feeding amounts of the two feeders to improve the combustion conditions, combusting the biomass fuels by adopting the biomass vaporizing chamber and the gas-powder mixed chamber. The invention has the advantages that the possibility that a volatile matter is split into black carbon difficult to combust is lowered, thus the phenomenon of emitting black smoke is decreased, and the existing biomass boiler combustion efficiency is improved.