In the traditional view the ultimate goal of mission was to build up the indigenous church which can stand itself carrying out self- govercúng, self-propagating, self-supporting. For this reason the three-self princip1e was considered the most crucial principle in mission strategies. At 1east until 1950s there was almost no one who doubted or opposed the formula. Yet with the appearance of Mìssio Dei concept -- which emphasizes the "world" instead of the "church"-- in the 1950s, lots of criticisms fell on the three-self principle which specially focused on indigenous church. Finally in these days the three-self principle seems to be considered an antique or useless concept not drawing any interest. This article started from the question why this change occurred and whether this kind of negative view toward the principle is proper or not. With the concern fìrst I invesstigate the major contents of the three-self formula to find out the strengths and weaknesses of the principle. Then evaluating all the criticisms on the principles whether or not they are proper，I found out that it is hard to accept some criticisms though some are valid. on the contrary to the negative view on the principle, I recognized that the principle is still very useful with lots of strong points and wisdoms for effective church planting ministry in the mission fìeld. Of course, the three-self principle is not the perfect mission principle as all others are not either. The principle is not the unique answer for solving problems in today’s mission either. In addition there might be some mission fìelds where it is hard to apply this formula exactly. However, I recognized that the three-self principles is very effective in building up healthy churches. Some scholars in the liberal wing tend to see church planting in the misslon fìeld as the act of imperialistic rnission. However, it is impossible to think of mission without church, since having Christian faith without community is impossible. One of the most serious problems in many mission fìelds today is the churches that rely only on missuibaries. There are so many churches that cannot stand well without the help of missionaries though they started 10 - 20 years ago. The worse thing is that there is a high possibility that these churches would dose their doors or be changed to other purposed-building easily as soom as missionaries leave the place. Furthermore, since the church is fragile, so are the seminaries also. The churches cannot provide canclidates for future pastors to the seminaries due to the lack of people, and lifewise the seminaries cannot send good pastors to the church either. As a result of this, as we can easily expect，the vicious cycle is continued, and the people in the mission field getting relying on missionaries more and more. so the missionaries cannot leave the rrusslon field though there are thousands of places where the more urgent needs are existing. In our missionary enterprises, all our resources and times are limited Considering the wide mission fields and the people’s needs there, we cannot but evaluate the effectiveness of our missionary works. Three- self principles provides abundant ideas and guidelines to the missionaries desiring to do effective ministries in the misslon fields. If we refer to the three-self principles and try to apply the id않s drawn from the formula, our missionary works would be much more effective in building up churches that grow up strongly and transform their society faithfully.