Real-time holographic interference patterns of three-dimensional distribution of gas refractive index in an incandescence lamp during its lighting process are introduced here briefly. Based on the fundamental physical problems occurred in gas heating process by filament, a concise physical and mathematical model has been developed. The forming processes of holographic interference pattern are studied numerically by using digital image processing technique. The obtained results have shown that when the refractive index outside of filament has a non-uniform distribution, the information of this non-uniform distribution can be reflected by the interference pattern in the projection of lamp, and the measurements of the fringes of interference pattern can be used to modify the real measurement data. Moreover, based on the result of study and the holographic computed temography (CT) technique, an example of the three-dimension distribution of gas refractive index inside an incandescence lamp is given without the influence of the change of refractive index outside of the lamp.