Period change of binary system V1799 Orionis in this work used 0.5 meter reflecting telescope with CCD photometric system in blue, visual and infrared bands. This research was observed at Thai National Observatory, Chiang Mai. A light curve of V1799 Orionis was analyzed using program Maxlm DL5 and its period change was also calculated. The results shown that its orbital period and a continuous weak increase at a rate are 0.29031 day and 6.43876 millisecond per year, respectively. Evolution of V1799 Orionis is corresponding to Thermal Relaxation Oscillation theory.
Keywords : Binary system: Period change: V1799 Orionis: Thermal Relaxation Oscillation