  One-loop on-shell and off-shell decays $H\rightarrow VV$ with
$VV=\gamma\gamma, Z\gamma, ZZ$ are presented in this paper. The effects of
one-loop on-shell and off-shell Higgs decays in Higgs productions at $e^-e^-$
collisions are also then examined. We find that the impacts of one-loop Higgs
decays are significant and they are must be taken into account at $e^-e^-$
collision.
