The key problem in the filed of the thin films electroluminescence (EL) display is how to get the high brightness blue emission. In order to design and control the EL device properties of diamond thin films, understanding of its blue emission mechanism is essential.In this paper the mechanism of the electroluminescence (EL) of the boron doped, double doped and Ce3+ doped diamond thin films have been investigated systemically, and the blue light emission with a maximum luminance of 3.5cd/m2 was observed from a diamond: Ce doped thin film electroluminescence (TFEL) device.1. Boron-doped diamond thin films ELThe high quality boron-doped polycrystalline diamond thin films have been produced by using plasma assisted CVD, and the solid 8203 act as dopant source. The boron impurity concentration in the diamond films was not exactly determined, but was controlled by changing the quantity of 6203 dopant from 0 to 6mg. Base on this, diamond thin films EL device with different structures have been made.For the diamond thin films EL device, which with single layer structure, the EL spectral peak is at 430nm,in the blue region. The emitted light intensity increased with the increasing of the 8263 dopant source while the quantity of 8203 less than 3.ling, furthermore after the quantity of 8203 is more than 3.1mg the resistivity of the device decreased rapidly so that the device have been broken.The spectral main peak at 380nm, in the ultraviolet region, have been obtained from the diamond thin films EL device, which with three layer structure.2. Boron and nitrogen doped diamond thin films ELThe experimental result indicated that the intensity of EL increases obviously and the threshold voltage (Vth) decreases with increasing nitrogen impurity within our doped level. The spectrum main line lay in blue- ultraviolet region (peaks at 470nm) to light-nitrogen-doped (the nitrogen concentration is less than 0.3%)diamond EL devices. Different from this, to heavy-nitrogen-doped (thenitrogen concentration is more than 0.3%) diamond EL devices the main line lay in yellow region (peaks at 584nm). Furthermore the yellow region EL intensity can get 5cd/m2, is much higher than that of the light-nitrogen-doped samples.3. Ce3+ doped diamond thin films ELCe3+ doped diamond thin films have been made by using sandwiched a CeFa layer between the two diamond films layers. Light emission with a maximum luminance of 3.5cd/m2 was observed from the diamond:Ce thin film electroluminescence (TFEL) device at an applied voltage of 150V, and the life is more than 10 hours. The electron-luminescence spectrum at room temperature showed the main peaks centered at 451nm and 494nm are attributed to isolated emission centers of interstitial of Ce + ions.4. Ce3+ ion implantation diamond thin films photoluminescence (PL)Ce3+ ion implantation diamond thin films, with two kind of dosage, have been made. Its PL character have been investigated, and the experiment result indicate that the PL spectrum showed the main peaks centered at 462nm,the other weaker peak at 421nm. The intensity of PL increases obviously with increasing Ce3+ ion implantation.To our knowledge, until now none reports on Ce3+ doped diamond thin films EL or PL have been published in the world, and our experiment show that Ce3+ can increase the blue light emission of diamond thin films effectively. Furthermore the results of the research indicate that the Ce3+doped diamond thin films stand a good chance is a perfect approach to resolve the EL blue emission.