This paper aims to examine the theological world of Professor Sang-Hyun Yoo. He has been raising many students since 1993, teaching New Testament at Yonsei University. Especially, he devoted his life to the study of the Acts of the Apostles, and published many writings and articles about it. Putting all his writings together, it becomes an Acts commentary. His theological characteristics are as follows below:<BR> 1. Professor Yoo pursues rational-biblicalism. He examines the traditions of the church to make rational-biblicalism understandable. Biblicalism depends on the foundation of the mere Scripture. <BR> 2. Professor Yoo’s writing style is the same as Luke’s writing style. If we read the book of Acts, we can draw a clear picture of the early 1st century church. Likewise, when you read Yoo’s books, you can see the characters and events that appear very realistic.<BR> 3. Professor Yoo emphasizes prayer most among all subjects, a unique trait that only theology has. So he studies for prayer, which is the central theme of the book of Acts. This is like his confession of faith that he can not understand the deep, profound spiritual treasures that God tells us without prayer.<BR> 4. Professor Yoo’s theology reflects the spirit of Yonsei theology that serves the Korean church and pastors. Theological writings of the university are sometimes not as practical that they are ignored by the general public and the church. To overcome this, Yonsei Theology has created the “Yonsei Theological Library,” and is making efforts to publicize and popularize theology. Paul’s Last Journey(2014) published by professor Yoo was the second book from the Yonsei theological Library series.<BR> Professor Yoo’s perspective of the book of Acts is that with the help of the Holy Spirit, the Gospel overcomes all adversities and spreads from Jerusalem to the Ends of the Earth(Acts 1:8). Likewise, Professor Yoo walked firmly for the Gospel and Yonsei spirit of truth and freedom. That’s why we call him a theologian of freedom for soul and life.