  Some recent studies have examined the gamma-ray flux profile of our Galaxy to
determine the signal of dark matter annihilation. However, the results are
controversial and no confirmation is obtained. In this article, we study the
radio flux density profile of the M31 galaxy and show that it could manifest a
possible signal of dark matter annihilation. By comparing the likelihoods
between the archival observed radio flux density profile data and the predicted
radio flux density profile contributed by dark matter and stellar emission, we
can constrain the relevant dark matter parameters. Specifically, for the
thermal annihilation cross section via the $b\bar{b}$ channel, the best-fit
value of dark matter mass is $\sim 30$ GeV, which is consistent with the
results of many recent studies. We expect that this method would become another
useful way to constrain dark matter, which is complementary to the traditional
radio analyses and the other indirect detections.
