It is essential that we have appropriate missions to share and communicate the Gospel, and to understand the interests, needs and world views of those we are trying to communjcate with. However, the big issue of today's missions seems to be the problem of cotextualization. During the mission history of two thousand years, there were so many experiences and attempts of the cross-cultural missions, questions like, "How the Gospel can be communicated effectively and relevant" figure prominently in the discussions of contextualization. The old forms or pre-stages of contextualization are accommodation, adaptation, and indigenization. It is enough to note some of that kind of approach, i.g. the missions of Mateo Ricci , Roberto de Nobili, etc. Although there has been much work on the subject of contextualization, the author will trace in this paper the historical background and theory of the contextualization. and try to show contextualization as a paradigm shift in mission theology. Then the author suggests to consider the theoretical basis of the contextualization, like principles, I) creative tension or complementarity of Gospel and cu ltures, 2) "indigenizing principle and pilgrim principle", 3) "critical contextualization", and "transcultural or supral cultural theology", and 4) "the prophetic, hermeneutical, and personal challenges of contextualization." However, contextualization is not the only method of missions, it has also limitations. Contextualization of the Gospel should be always reflected and reaffirmed in the process of mi ssions, by the "the international hermeneutical community"( ecumenical co-worker and local church leader, missionary and theologian), with the principle of theologia viatorum.