The invention discloses a combustion furnace for biomass fuel. The combustion furnace comprises a furnace body; supporting bases are arranged at the top of the furnace body; a combustion chamber is arranged in the furnace body; a base plate is arranged at the bottom of the combustion chamber; a feeding mechanism is arranged on the upper part of the side wall of the furnace body; and an ash accumulating plate is arranged at the lower part of the combustion chamber. According to the combustion furnace, the feeding mechanism is designed so that the biomass fuel can be conveniently fed into the combustion chamber under the condition that a container above the supporting bases is not moved away, in addition, the ash accumulating plate is arranged at the bottom of the combustion chamber, a spraying pipe is arranged above the ash accumulating disc and is used for spraying water into the ash accumulating disc so that ash generated after combustion of the biomass fuel can be pasty and can be conveniently subjected to subsequent treatment.