A series of torsion tests under different temperature were carried out with circumferential notched cylindrical rock specimens. By this kind of specimens, mode III rock crack propagation in real meaning was realized. The initiation torsion M of the mode III rock crack was measured under different temperature. The variation law of M v.s. temperature T was obtained. The initiation stress near crack tip under different temperatures was calculated by finite element method, and then, the mode III fracture toughness KIIIC of the rock was obtained by further calculation. The experiment and numerical results show that the mode III fracture toughness of the rock decreases with the temperature increase. The results of the paper can be used in the design of deep underground engineering ,disaster prevention and mitigation engineering.