Embodiments of the present disclosure provide an apparatus and method for detecting channel spacing and a system. The apparatus for detecting channel spacing includes a first estimating unit configured to estimate a frequency offset of a center channel according to a received signal, a second estimating unit configured to estimate a frequency offset of a neighboring channel according to the received signal, and a determining unit configured to determine channel spacing according to the frequency offset of the center channel estimated by the first estimating unit and the frequency offset of the neighboring channel estimated by the second estimating unit. With the embodiments of the present disclosure, estimation accuracy of channel spacing may be ensured, and influence of non-ideal factors on estimation value may be reduced.