The invention discloses an exploitation method of coal seam gas in a low-permeability coal seam, and belongs to the field of coal seam gas exploitation. The method includes the steps: determining themaximum principal stress direction of the low-permeability coal seam; arranging at least two large horizontal lane wells in the low-permeability coal seam; arranging a plurality of production wells intwo sides of a horizontal section of each large horizontal lane well among the large horizontal lane wells; exploiting the coal seam gas in the low-permeability coal seam by the large horizontal lanewells and the production wells. The diameter of each production well is smaller than that of the horizontal section of each large horizontal lane well. By the aid of the horizontal sections of the large horizontal lane wells perpendicular to the maximum principal stress direction, release of stress in the low-permeability coal seam is promoted, more crack channels are formed, the coal seam gas isexploited by the large horizontal lane wells and the production wells, and the exploitation efficiency of the coal seam gas in the low-permeability coal seam is improved.