This article is to explore the minimum length of confidence interval of F distribution. In 1975, Crisman had mentioned a bisection method to calculate the confidence interval with the minimum length about the Chi-Square distribution to meet the desired critical values. This paper will first explore Crisman’s research and applies the same method on F distribution to find the confidence interval with minimum length, finally we will provide a SAS Macro program and use some examples to illustrate how to use it.