The invention provides low-concentration sulfur hexafluoride gas recovery device. The recovery device comprises a mixed gas inlet, a first compressor, a second compressor, a storage tank, a first two-site three-way valve, a second two-site three-way valve, a third two-site three-way valve, a fourth two-site three-way valve, a first electric butterfly valve, a second electric butterfly valve, a nitrogen inlet, a nitrogen outlet, a sulfur hexafluoride gas recovery opening, a first molecular sieve, a second molecular sieve and a sulfur hexafluoride gas detector; heating rods are uniformly arranged in the first molecular sieve and the second molecular sieve; pressure meters are connected with the first molecular sieve and the second molecular sieve. The invention also discloses a recovery method for the low-concentration sulfur hexafluoride gas recovery device. According to the invention, by adopting a principle of adsorbing SF6 gas by a molecular sieve, the adsorption quantity can reach 50 percent of the weight of molecular sieve, by adopting characteristics of regeneration of pressure-reducing heating, the tail gas exhaust with a standard, the pollution to air can be reduced and environment protection requirements are met. Compared with membrane separation device, the device has advantages of economy and implementability.