Through computer simulated process of Coating deposition, we find that IAD (ionassisted deposition) technique can improve the density, adherence and optical properties of thin films. However, the high energy ion beam may result in a large absorption of film materials and thus makes the technique useless. It has been found that the low energy, high current density ion beam is a most promising technique in the field of optics of thin films by independent researches on theory and experiment, respectively.