Negative-charged ion energy spectra of the Fe_3O_4 (001) and (111) surface revealed large peaks attributed to the O^- recoils from a binary collision. Under Ar^+ ion bombardments such an emission was largely affected by the screening effect of the Fe ions. A distinguished peak related to the O^+ recoil ions was observed under Ne^+ ion bombardments, while such a peak was merged into the high background in the case of Ar^+ ion ones. A weak effect from the Verwey transition was found on oxygen emissions. For the (111) surface a small peak characteristic of the O^+ recoils from double collisions appeared in the energy spectra around 140-170 K and a minimum was observed in both R^+(T) and R^-(T) curves under 6 keV Ne^+ ion beam.