The invention discloses a gasification method and gasification furnace of 
coal seams based on 
branch wells, and aims to solve the problems that a gasification technique of 
coal seams is high in cost and low in 
recovery ratio in the prior art. The gasification method comprises the following steps: after finishing drilling construction, enabling gasification channels to be run-through, respectively downwards placing packers or guidance devices in different 
branch wells, downwards placing gas injecting devices in corresponding 
branch wells through the guidance devices, injecting a gasifying agent, confirming the gasifying time of 
coal seam regions to be gasified through calculation, and completing the gasifying process of the coal seam regions to be gasified; replacing the packers or the guidance devices in the branch wells, completing the gasifying process of the coal seam regions to be gasified of all branch wells, and outputting generated 
fuel gas to the ground through gas exhaust wells. Through the adoption of the gasification method disclosed by the invention, the fixed point quantitative controllable injection of the gasifying agent is realized, the process of gas generation is stable, the demands of the 
deep processing of 
fuel gas are satisfied, the gasification 
coal mining output and the 
recovery ratio of single well are effectively increased, besides, the service life of each gas 
injection well is prolonged, the cost of building furnaces and drilling is reduced, and the cost of ground construction and operation is reduced.