In 1946, he entered began studying aesthetics at Seoul National University, but left and returned to his hometown during the Korean War in 1950.
In 1954, Jang established the Dae-Sung school in Wonju in order to pass on the teachings of An Chang-ho, and participated in the One World Movement, comparing notes with Albert Einstein.
In 1971, he joined a street demonstration for social justice and struggled against the despotism of Park Chung-hee with Catholic bishop Ji Hak-soon.
In 1989, he built a monument to Dong Hak's second leader, Choi Shi-hyung, in Hojeo-myun, Wonju, where he was arrested by government troops.
In 1993, he published a book, Lao-tzu Story Of Jang Il-soon, which analyzed his views of life, with the help of minister Lee Hyun-ju.