The control system is an original and sound system of this Country. The Founder of this Country, Dr. Sun Yat-sen, proposed after he established this Republic that the control power should be practiced by an independent body to highlight the functions of such power, rather than putting it under the legislative power as in the 3-Separated Powers common to many Western countries. This thesis begins by examining the status and nature of control power in the 5-Separated Powers as in the constitutional regime of this Country from a perspective of separation of powers. It follows by exploring the evolution of mandates of the Control Yuan as a result of various constitutional amendments during the 1990s when the Government undertook constitutional amendments engineering for the promotion of democratic development. This thesis then analyzes the impact of such constitutional amendments upon the practice of control power from existing laws and regulations relevant to the control power and provides the views of this author. It then analyzes the status quo of the practice of functions of the Third Control Yuan by its Members, in comparison to the statistics on the functional practice of the Second Control Yuan, so as to comprehend the efficacy of the practice of functions of the Third Control Yuan. In the conclusion, the author puts forward his own findings and suggestions on the practice of control power by the Third Control Yuan.