The invention discloses a method for testing coal seam in-situ anisotropy main permeability in a field condition by comprehensively utilizing downhole crack observation, underground geostress survey and the indoor permeability experiment. The method performs observation for the crack distribution of a coal seam by adopting a digital panoramic drilling camera system, the coal seam ground stress ismeasured by adopting a stress relief method, sample collection is performed on the basis of the crack observation, and the permeability experiment loading is performed on the basis of the ground stress observation. The method for testing coal seam in-situ anisotropy main permeability overcomes the blindness of sample selection direction in the previous coal seam permeability determination, increases the reduction degree of permeability experiments on site, and provides a basis for mine gas extraction and treatment.