The invention belongs to the technical field of optical communication. In order to realize the simultaneous conversion of more wavelengths, the invention adopts the technical scheme that the device for converting wavelength division multiplexing (WDM) of a single-fiber loop into time division multiplexing (TDM) in a fiber sensor network comprises an annular fiber coupler, a fiber Bragg grating (FBG), an I/Q (In-phase/Quadrature) optical modulator and an erbium-doped fiber amplifier (EDFA) which are sequentially connected into a loop; an I/Q single side band (SSB) modulator is driven by a high-frequency radio frequency source and used for realizing the SSB frequency up-conversion; and the working frequency f of the high-frequency radio frequency source is set to be a formula in the specification, wherein delta lambda in the formula is a wavelength interval in an input multi-wavelength spectral induction signal. The invention is mainly applied to converting the WDM of a single-fiber loop into the TDM in the fiber sensor network.