The invention discloses a rock permeability testing system. The rock permeability testing system is characterized by comprising a confining pressure control device (1), a rock core pressure chamber (2), a porosity measurement system (3), an upstream gas storage cylinder (4), a downstream gas storage cylinder (5), an upstream air pressure recording meter (6), a downstream air pressure recording meter (7), an upstream-downstream air pressure recording meter (8), a high-purity argon bottle (9) and a high-precision air pressure recording instrument (10). The invention further discloses a method for testing the permeability by utilizing the rock permeability testing system. The rock permeability testing system has the advantages that the operation is simple, the to-be-measured physical quantity is little, and the measurement range is wide; the system can be used for measuring normal rocks with the permeability higher than 10-15 m<2>, low-permeability rocks and even ultralow-permeability rocks, and the measuring precision reaches 10-24 m<2>.