A review of signal processing algorithms employing Wi-Fi signals for position-ing and recognition of human activities is presented. The principles of how channel state information (CSI) is used and how the Wi-Fi sensing systems operate are reviewed. It pro-vides a brief introduction to the algorithms that perform signal processing, feature extrac-tion and recognitions, including location, activity recognition, physiological signal detec-tion and personal identification. Challenges and future trends of Wi-Fi sensing are also discussed in the end.