A remote fiber Bragg grating (FBG) sensors system based on the self-heterodyne detection and wavelength-sweeping technique is proposed and experimentally demonstrated. In this system, the heterodyne signal produced by the reflected sensing signal and the local reference beam is detected by a balanced photodetector. With frequency-shift and pulse-modulation of the acousto-optic modulator, the detection sensitivity and sensing distance are improved effectively. The system is able to detect the two multiplexed FBGs placed 171 km away, offering a signal-to-noise ratio of 33 dB without amplification. In addition, this system can scan the reflection spectra of FBGs accurately. Applying this system to remote temperature detection, the results show the typical liner behavior of both FBGs, shifting their reflected Bragg wavelengths in 11 pm/℃.