Biomass greenhouse heating boiler

The invention discloses a biomass greenhouse heating boiler, and relates to a gasifier, aiming at solving the problems that the existing gasifier is limited in the primary combustion, low in calorific value and small in heating area of being within 100m , wherein a combustion cylinder is vertically fixed in the center of the upper head face of a grate; an umbrella hat is arranged at the top of the combustion cylinder; a circular-truncated-cone-shaped upper cylinder body, a circular-truncated-cone-shaped middle cylinder body and a circular-truncated-cone-shaped lower cylinder body are sequentially arranged in the furnace body from top to bottom; a cavity which is formed between the circular-truncated-cone-shaped lower cylinder body and the furnace body is an annular air duct; 6-10 vent holes are uniformly distributed in the circular-truncated-cone-shaped lower cylinder body along the same circumference; the output end of a spiral conveyor is arranged above the input end of a material groove, and the input end