The fiber-optic slip-ring, consisting of two collimator lenses and realizing the off-axis rotating connection, as a new passive device proposed and connects with the optical fiber Bragg grating sensor is used to detect the temperature on the rotating parts when its axis is occupied or the shaft is hollow. The main influence factors of the insertion loss of the device are analyzed, theoretically. Simulation results show that the insertion loss is highly sensitive both to the transversal dislocation and the axial angle between two collimator lenses, while it is slightly insensitive to the change of the axial distance. Experiments show that during the rotating parts uniformed, the received signals through fiber-optic slip-ring are the periodic pulse signals, and the duty cycle of which is 0.5%, corresponds with the result of simulation. Using fiber-optic slip-ring coupling for fiber Bragg grating sensing light path, to achieve the change of temperature on the rotating part real-timely during heating the temperature field, the feasibility of this measurement method is verifies.