The invention discloses a single-frequency fiber laser device with a wide single-longitudinal-mode temperature range. The laser device is composed of a broadband fiber grating, a highly-doped gain fiber, a narrowband fiber grating, a wavelength division multiplexer, a single-mode semiconductor pump laser device and an optical isolator. The single-mode semiconductor pump laser device is used as a pump source to carry out pumping on a resonant cavity; with the fiber grating with the short grating zone length, the reflectivity of the narrowband fiber grating is optimized and improved; and with the ultra-short highly-doped gain fiber as a grain medium, the effective cavity length of the whole resonant cavity is shortened effectively from many aspects and the space between adjacent longitudinalmodes inside the cavity is increased substantially, so that the laser device is able to realize a stable single-frequency laser output within a wide temperature range. The laser device has the wide single-longitudinal-mode temperature range and is protected from being affected by the external environmental temperature in operation; and the stable single longitudinal mode output is realized. The laser device can be applied to fields of space detection, coherent optical communication, Doppler wind-finding radar, gravitational wave detection, and quantum optics and the like.