Covert channel is the communication channel that allows a process to transfer information in a manner that violates the system’s security policy. It is a major threat to the secure information systems and widely exists in secure operation systems, secure networks and secure database. Covert channel analysis is generally required by secure information systems’s secure criterion, such as TCSEC. This paper firstly analysis the covert channel concept, field, techniques and classification. Next, it surveys the classic techniques and methods from the following aspects: covert channel identification, measurement, elimination, limitation, auditing, and detection. The research achievements in the past 30 years are systematically concluded, especially the new techniques of covert channel measurements and handlings in recent years. This paper attempts to give a comprehensive and clear outline for this research direction, and provides a useful reference for the researchers of this field.