Rotary steerable system (RSS) is a new technique of drilling technology adopted in directional drilling. Compared with conventional directional drilling, RSS has the ability to improve the drilling efficiency, reduce the drilling risk and decrease the drilling cost at the same time. This paper summaries the fundamental structure, classification, directional principle and development process of RSS; and gives detail analysis of the control methods in RSS. According to these summaries and analyses, the advantages and disadvantages of RSS at present are given, and some key suggestions about this technique and the related control methods are also proposed in this paper.