  The ultracompact minihalos could be formed during the earlier epoch of the
universe. The dark matter annihilation within them is very strong due to the
steep density profile, $\rho \sim r^{-2.25}$. The high energy electrons and
positrons from the dark matter annihilation can inverse Compton scatter (ICS)
with the background photons, such as CMB photons, to acquire higher energy. On
the other hand, the synchrotron radiation can also be produced when they meet
the magnetic field. In this paper, we study the signals from the UCMHs due to
the dark matter annihilation for the radio, X-ray and $\gamma$-ray band. We
found that for the radio emission the UCMHs can provide one kind of source for
the radio excess observed by ARCADE 2.
  But the X-ray signals due to the ICS effect or the $\gamma$-ray signals
mainly due to the prompt emission from dark matter would exceed the present
observations, such as Fermi, COMPTEL and CHANDRA. We found that the strongest
limits on the fraction of UCMHs come from the X-ray observations and the
constraints from the radio data are the weakest.
