This study compares St. Nicholas' Orthodox Church in Seoul (1968) and St. Dionysios' Orthodox Church in Ulsan (2005), which are Byzantine-style churches under the Korean Orthodox Church, with Hagiya Sophia in Istanbul, a masterpiece of Byzantine architecture. Focusing on the construction method and shape of the dome, which is a major characteristic of Byzantine architecture, this study compares the architectural background of these three churches, the presence and shape of the dome, the presence of drums, and the number and shape of skylights. As a result, it was found that these three churches differ in the construction method of the dome due to differences in different architectural backgrounds and structural methods, and that these structural and morphological differences ultimately determine the atmosphere of the interior space of the cathedral. This study examines two representative Byzantine Orthodox churches in Korea, both designed by the same architect, Zho Chang Han (b. 1936), with a time gap of approximately 40 years between them. It holds particular significance in exploring how the Byzantine dome was constructed differently by analyzing the historical context and structural characteristics of the Orthodox Church.