The invention provides a low permeability coal seam electricity explosion vibration and microwave assisting liquid nitrogen freeze-thawing permeability increasing device. The low permeability coal seam electricity explosion vibration and microwave assisting liquid nitrogen freeze-thawing permeability increasing device comprises a pulse discharging reactor, a cable, a high voltage pulse generator,a fracturing pipe, a mining pipe, a high pressure rubber pipe, a microwave transmitter, a coaxial waveguide, a microwave converter, a microwave generator, a first hole packer, a second hole packer, anitrogen inflating pipe, a water box, a high pressure water pump, a liquid nitrogen pump and a liquid nitrogen tank. The invention further discloses a low permeability coal seam electricity explosionvibration and microwave assisting liquid nitrogen freeze-thawing permeability increasing method. A hydraulic fracturing technology, an electricity explosion vibration technology, a liquid nitrogen freeze-thawing technology and a microwave technology are harmoniously integrated, the permeability and the porosity of a coal seam are increased to a great extent, coal seam fractures can be increased, the liquid nitrogen freeze-thawing efficiency is improved, circular work is conducted, ice in the fractures is easily molten, the permeability of a low-permeability coal seam is greatly improved, the effect of mining and exhausting methane gas is improved, expected time needed for mining the methane gas is shortened by a large margin, and a superior premise is provided for mining the methane gas ofa mine.