期貨市場交易機制的運行是以保證金為核心，因此如何設計一合適之保證金水準，對交易所而言是十分重要的課題，保證金水準的設定不僅要考慮自身可能面臨的違約風險，還需考量市場的流動性，另外台灣股市有7%漲跌停限制，期交所在設計最適之保證金水準時，必需將此一限制因素納入考慮。本文依據Broussard（2001）的作法，並以台股期貨、金融期貨和電子期貨等三種期貨契約為標的，探討在不同價格限制下之期貨保證金水準之違約機率的差異。經由實證結果發現：（1）7%價格限制條件比6%和5%價格限制條件所設算出的違約機率高，這種現象的產生是由於7%價格限制條件可容忍較大的價格變動之故；（2）以期貨日內價格最大值減最小值，因隱含較大的價格波動，故在相同之保證金水準下，較其他計算方法得到較大之違約機率；（3）電子期貨因波動性較大之緣故，在相同之保證金水準下，違約機率高於台股期貨和金融期貨。

　　　　　It is a very important issue for the futures clearinghouse to design the appropriate margin because the operation of the whole futures markets is dependent upon the margin mechanism. The setting of appropriate futures margin must both consider the probability of default risk and the liquidity of the futures market. Meanwhile, there are 7% price limits in TAIFEX futures contracts, it must include this special constraint for the design of appropriate futures margin. This paper explores the method proposed by Broussard (1999) to design the appropriate margin levels for the domestic futures contracts, and shows the default probability under different kinds of margin levels. The evidences show that : (1) In 7% price limits constraint, the default probability is higher than the price limits of 6% and 5% ; (2) The extreme data calculating from intraday highest-to-clear futures price indicates the highest default probability under the same margin level；(3) The electronic sector index futures should set the highest margin level because of its highest volatility.