  Radio observation is crucial to understanding the wind mechanism of OB stars
but very scarce. This work estimates the flux at 1450MHz ($S_{\rm 1.4GHz}$) of
about 5,000 OB stars identified by the LAMOST spectroscopic survey and
confirmed by the Gaia astrometric as well as astrophysical measurements. The
calculation is performed under the free-free emission mechanism for wind with
the mass loss rate derived from stellar parameters. The estimated $S_{\rm
1.4GHz}$ distributes from $10^{-11}$Jy to $10^{-3}$Jy with the peak at about
$10^{-8}$Jy. This implies that the complete SKA-II can detect more than half of
them, and some tens of objects are detectable by FAST without considering
source confusion. An array of FAST would increase the detectable sample by two
orders of magnitude.
