Randomized controlled trial （RCT）, considered as the strongest evidence-based method in clinical trial, can provide first-hand scientific evidence for clinical practice and instruct clinicians to make correct decisions in practice. This article introduces the principles for RCT designing, analyzes the common problems concerning RCT in clinical practice and the common mistakes made in RCT statistical methods. It is concluded that application of RCT method and correct statistical methods are of great importance in clinical medical research.