Based on the density functional theory DFT/ B3LYP at 6-311g level, the ground states of BeO molecule are optimized. The effects of electric field on the bond length, the system energy, the charge distribution, the energy levels, the HOMO-LUMO gaps and the infrared spectrum of BeO molecule are studied. The results indicate that the bond length of BeO molecule increass,but the system energy decreases as the external electric field increases from 0.0 to 0.05 a.u. At the same time, the energy gaps between the HOMO and LUMO become separated with the increase of electric field. It shows that the structure of BeO molecule is steady under external electric field so that oxygen atom in BeO is difficult to combine with hydrogen atom escaping from the reactor.