We study the onset of neutron drip in high density matter in the presence of magnetic field. It has been found that for systems having only protons and electrons, in the presence of magnetic field 10 15 G, the neutronization occurs at a density which is atleast an order of magnitude higher compared to that in a nonmagnetic system. In a system with heavier ions, the effect of magnetic field, however, starts arising at a much higher field, 10 17 G. These results may have important implications in high magnetic neutron stars and white dwarfs and, in general, nuclear astrophysics when the system is embedded with high magnetic field.