To improve the reliability that are very important for large-scale and long range all optical fiber sensor networks, monitoring optical fiber sensor networks is necessary. We proposed a novel method for monitoring optical fiber sensor networks using optical frequency-domain reflectometry (OFDR) which provides a narrow spatial resolution that enables us to locate closely separated reflection and discrete sensors such as fiber sensing grating and other microstructure fiber sensors. Moreover, thanks to the inherently coherent detection, a high dynamic range can be realized that allows the measurement of Rayleigh backscattering throughout a fiber network. Namely, OFDR also can monitor distributed fiber sensors By using narrow linewidth laser, OFDR's monitoring range satisfies the requirements for long range optical fiber sensor networks. In our OFDR system proposed, we can achieve to monitor optical fiber sensor networks with measurement range of a few tens of kilometers in a sub-cm spatial resolution.