  Recent years have witnessed tremendous progresses in creating and
manipulating ground-state ultracold polar molecules. However, the two-body loss
regardless of the chemical reactivities is still a hurdle for many future
explorations. Here, we investigate the loss suppression of non-reactive bosonic
$^{23}$Na$^{87}$Rb molecules with a circular polarized microwave blue-detuned
to the rotational transition. We achieve suppression of the loss by two orders
of magnitude with the lowest two-body loss rate coefficient reduced to
$3\times10^{-12}~\rm{cm^3/s}$. Meanwhile, the elastic collision rate
coefficient is increased to the $10^{-8}~\rm{cm^3/s}$ level. The large
good-to-bad collision ratio has allowed us to carry out evaporative cooling of
$^{23}$Na$^{87}$Rb with an efficiency of 1.7(2), increasing the phase-space
density by a factor of 10. With further improvements, this technique holds
great promises for creating a Bose-Einstein condensate of ultracold polar
molecules.
