Security is an essential requirement for cloud computing. However, how to protect critical applications and data in cloud computing and prevent platform administrators from violating user privacy is still an unsolved problem. In 2013, Intel proposed SGX, a new processor security technology which can provide trust zones on a computing platform to ensure the confidentiality and integrity of key user code and data. As a major research progress in the field of system security, SGX has a very important significance for system security, especially the security protection of cloud computing. In this paper, the mechanisms and properties of SGX are introduced, the key principle and technology are analyzed, and the side-channel attack and defense against the SGX technology are presented. Meanwhile, the paper surveys the state of the art of SGX and compares it with other trusted computing technologies. Finally, the research challenges and the future application requirements of SGX are suggested.