Hongam (Na Chol, 1863-1916) initiated Tan’gun’gyo in 1909 and reestablished it as Taejonggyo, an indigenous religion of Korea, in 1910 in order to spread the Tan’gun faith under Japanese colonialism. Hongam accepted Paekbong’s religious movement of Tan’gun faith which was active in the Paekdu mountain and newly systematized the doctrine of the Samwi-ilch’e, the trinity of three gods. He considered Tan’gun not as a mystical person of the National Foundation myth of Korea but as a historical person and a heavenly being who founded the Kingdom of Kojoson (Old Korea). Hongam performed the ritual of Son or the Heavenly ritual serving to Hanim at the Sams ngsa shrine at Guw l mountain in 1916. This became the main Heavenly ritual in Taejonggyo. During the ritual, all the participants adhered to the religious taboos and performed the ritual in the area of the sacred mountain during the specified sacred time of the full moon day, also known as August 15 in the lunar calendar. They participated symbolically in the process of recovering oneness with the Heavenly Being, thereby becoming part of the essence of the cosmos. The archetype of the Tan’gun faith can be demonstrated in the Heavenly ritual. In this research, I will examine how Taejonggyo adopted and transmitted the Tan’gun myth. Also, I will do my research on the symbolic system of the Heavenly ritual concerning religious taboos; the sacred nature of time and space; the alteration of the tablet of the three gods; the faith in the trinity of the three gods; the characteristics of the Korean centrism; and Hongam’s sacrifice of his life.