The invention discloses an optical-fiber online temperature measurement probe device including a detector module outline structure and an optical-fiber detector module in the detector module outline structure. The detector module outline structure is a housing in shape and pouring sealant is filled between the detector module outline structure and the optical-fiber detector module; the optical-fiber detector module is connected with a host system through an optical fiber; a high-temperature resistance insulation material is adopted in the detector module outline structure; and the detector module outline structure and a contact arm of a transformer substation device to be detected are fixed through a casting method. The advantages of the technical scheme of the invention are that through adoption of a structure in which the optical-fiber detector module and dynamic and static contacts of the transformer substation device to be detected are surrounded and fixed by the detector module outline structure and form an integral part through casting, an original transformer substation device is enabled to have functions of temperature measurement and real-time monitoring at the same time; and anti-interference, radiation-resistance and high-pressure resistance performance of the temperature measurement probe device is strengthened. Moreover, temperature acquisition sensitivity is improved and site operation and installation steps are simplified.