Clear Air Turbulence (CAT) is one of extremely dangerous weather for aviation safety. CAT often takes place without visual weather phenomenon and cannot be detected by present airborne radar. CAT poses so great threat on aviation safety that researches on formation mechanisms and early warning and forecasting of CAT becomes quite necessary. The recent advances in CAT researches are reviewed and summarized by classified into three aspects: formation mechanisms, observing measures, and forecasting methods. There are some significant advances such as the important role of inertia gravity waves in CAT formation, valuable observations provided by new detecting methods, CAT numerical forecasting based on turbulence indices, and so on. Then, aspects which need to be improved further are analyzed, and the trends of researches on CAT are also prospected.