In a system of electron assisted hot filament chemical vapor deposition, nanocrystalline diamond films were deposited at 1kPa reaction gas pressure with different bias current. The films were characterized by X-ray diffraction, field emission scanning electron microscope and semiconductor characterization system. With appliance of bias current, the films exhibit a pronounced preferential orientation of (110) planes and change of the surface morphology. When bias current is 8A, the deposited film displays finest grain and smoothest surface. Formation of preferential orientation of (110) planes and its influence on electrical properties of the films are discussed under the condition of electrons bombardment and lower reaction gas pressure.