Activity recognition has broad application prospects in many fields including pervasive computing and human-computer interaction. In this paper, the technology of wireless-based activity recognition is introduced. By using wireless signals, one can achieve non-line-of-sight recognition without carrying any devices. Also, it is easy to deploy a wireless-based recognition system due to the ubiquity of wireless communication system. The basic idea is that, as a specific propagation path is formed when the signal is blocked, reflected or scattered at body, one can detect the different characteristics of propagation that correspond to the distinct human behaviors. As a result, action recognition is performed by analyzing the distinguishable features of signal propagation. The basic principles and applications of wireless-based activity recognition are reviewed, and the challenges and related performance metrics are presented. Finally, open problems are discussed to point out the future research trends.