作為司法院大法官最主要的違憲審查基準，比例原則所面臨之質疑，一方面來自於其本身涵義與操作模式上，我國釋憲實務未能明確、清晰地運用；另一方面，則來自於留美學者援引美國法上三重審查標準，而質疑比例原則之審查，係僵硬、單一而無從保留立法空間的一種審查基準。為釐清後者的質疑，本文擬借助德國學者R.Alexy所開展之法律原則理論，加以闡述比例原則之規範結構與法律原則的特質；並且透過Alexy所分析憲法規範之結構性餘地與立法者之認識餘地，以證立在比例原則操作下，立法者仍有憲法規範上所肯認的結構餘地以及立法事實上的認定與預測優先地位，換言之，比例原則仍得以結合不同事實認定與預測的審查密度作為審查模式。

Principles of Proportionality, the major standard for the Justices of the Constitutional Court, Judicial Yuan to investigate the unconstitutional, has being challenged. First, our Grand Justices' constitutional interpretations cannot apply the meaning and the patterns of the principles of proportionality very clearly and definitely. On the other hand, the scholars who studied in the United States have cited Triple Standards of Review from the American Law. Thus, it challenged the Principles of Proportionality, which is an inflexible, single and has no space in legislation. In order to clarify the suspicions of the latter, this paper is written with the help of the academic principle of law, which was explicated by the German scholar--R. Alexy. By means of the, academic principle of law to explicate the structure of Principles of Proportionality and the characteristic of the principle of law. Though the Structural Discretion of the constitution standard which Alexy analyzed and Epistemic Discretion of legislators to prove that under the operation of the Principles of Proportionality, the legislators still have the acceptation in Structural Discretion and the first position to cognizance and presume of the legislative facts in constitution standard. 1n other words, Principles of Proportionality still can combine different cognizance and presumption of facts and Density of Canvass as a criteria to investigate.