Derivatives Market in Korea dates back to 1996 when KOSPI200 was launched as the first domestic derivative. Despite its short history, the derivatives market in Korea is now proud of the largest trading volume in the world thanks to the growing awareness on risk management after the Asian financial crisis. The margin requiring system is the most important and unique feature of futures market. And margin is sometimes used as a government policy tool of controlling the market activity. This article focuses on the fact that the change of the margin requirement which took place on 1997/7, 1997/11, 2000/2, 2001/2, 2003/3 have actually increased or decreased the volume of futures market. The following is a summary of the results of this study. First, increasing the margin requirement has reduced the volume of futures market and decreasing the margin requirement has nearly expanded the volume of futures market by graphic method. Second, the margin requirement changes always don't effect the volume of futures market significantly using intervention analysis.