  We suggest an approach for using microwave radiation in diagnostics of
ultracold neutral plasma. Microwave scattering from ultracold neutral plasma is
calculated . Simple formulations are get and indicate that the dipole radiation
power of ultracold neutral plasma does not depend on density profile $n_e(r)$
and $\omega$ when $\omega\gg\omega_{pe0}$, but on the total electron number
$N_e$. This method provides the information of $N_e$ and from which we can get
the three body recombination rate of the plasma, which is extremely important
in the researches of ultracold neutral plasma.
