Imperial Japanese Navy attacked Ta-kou Port on 15th October 1985. In this battle, first two Chinese characters on the inscribed board of Chi-hou Fort were smashed by naval vessels of Japan, only last two Chinese characters – “Tien-Nan” (天南) left on the inscribed board. It is clear that those characters on the inscribed board of Chi-hou Fort were not writed by Shen, Pao-chen (沈葆楨) after calligraphy examination. Ting, Jih-chang (丁日昌) and Tsen, Yu-ying (岑毓英) did not write those characters either, which was inferred from textual analysis. Those characters on the inscribed board might be writed by the army’s officers or engaged scholar of Ching Dynasty. It is hard to confirm due to lack of evidence. There are 4 ways of saying regarding Chinese characters on the inscribed board of Chi-hou Fort up to date, that are “Wei (威) -Chen (振) -Tien (天) -Nan (南)”, “Wei-Chen (震) -Tien-Nan”, “Wei-Chen (鎮) -Tien-Nan” and “Ti (砥) -Chu (柱) -Tien-Nan”. The saying of “Wei-Chen (震) -Tien-Nan” is wrong due to incorrect quoted from literature. “Wei-Chen (鎮) -Tien-Nan” and “Ti (砥) -Chu (柱) -Tien-Nan” are disbelief because of no reference source. The saying of “Wei (威) -Chen (振) -Tien (天) -Nan (南)” referred from a postcard of Yoshida photo studio (吉田寫真館), as well as a article of Chen, Hsi-ju (陳錫如) entitled “A travel to Chi-shan” (旗山記). Neither postcard nor article mention explicit information sources, the authenticity of this saying still need to prove. Therefore, throse characters on the Chi-hou Fort’s inscribed board is still a mystery as a result of no hard evidence has been found to confirm this saying.