With the rapid development of the low-altitude economy and the increasing proliferation of unmanned aircraft system (UAS) technologies,low-altitude security issues have become increasingly prominent. UAS possessing low, slow, and small characteristics, if used illegally in sensitive areas, will pose a severe threat to public safety, aviation order, and even national security. Therefore, developing efficient and reliable low-altitude counter-UAS technologies has become a critical support for ensuring the healthy development of the low-altitude economy. This study reviews the development status of counter-UAS technologies. It first sorts out non-cooperative airspace surveillance technologies, including radar, radio frequency signal monitoring, optic identification, and acoustic detection, summarizing the principles, advantages, and limitations of various sensing methods. Moreover, it explores the current research status of enhancing sensing capabilities through multi-sensor information fusion. Subsequently, from the perspective of cyber-physical systems, the study evaluates the technical characteristics and application challenges of counter-UAS measures at both a physical layer (e.g., lasers, microwaves, net capture, drone collision) and a cyber layer (e.g., communication jamming, GNSS spoofing, acoustic interference). The study indicates that current low-altitude counter-UAS technologies still face challenges in terms of detection and response. To address these challenges, this study proposes recommendations from a technological development perspective, including the adaption of sensing technologies to specific scenarios, pilot deployment of networked low-altitude surveillance equipment, optimization of counter-UAS measure combinations, in-depth research on counter-UAS mechanisms, risk management during counter-UAS operations, and multi-platform collaboration. This study aims to provide a reference for the development of low-altitude counter-UAS technologies through a systematic review, thereby contributing to the establishment of a safe, reliable, and efficient low-altitude security system and ensuring the sustained development of the low-altitude economy.