Carbon nanotubes (CNTs) films are very efficient cathodes for used in field emission devices, such as field emission displays. In this paper, the randomly oriented carbon nanotubes film was grown on silicon substrate by chemical vapor deposition (CVD) using a gas mixture of nitrogen, hydrogen and acetylene, the catalyzer is Ni film which was electroplated in the solution of NiSO4·6H2O and H3BO4 ( NiSO4•6H2O:50g/L; H3BO4: 15g/L) in deion water with and without added the Si(OC2H5)4. The SEM, TEM has been used in order to determine the structure of the films, which show that the diameter of the nanotubes would be decreased from about 100nm to 50~70nm when add the Si(OC2H5)4. Field emission characterization has been measured on the carbon nanotubes films-anode setup room temperature and in a vacuum chamber below 10-4 Pa. The Fowler-Nordheim plot shows a good linear fit, indicating that the emission current only comes from the protruded nanotubes. Threshold field strength of this nanotubes film is about 8 V m/μm for an emission current of 1 μA, and the most field emission current densities of more than 2 mA/cm2 are measured for 11 V m/μm. In addition, the bright light spot can be observed, while emitted electron bombardment fluorescent screen.