With the development of unmanned aerial vehicle （UAV） software and hardware technology， the flying Ad-Hoc networks （FANETs） formed by the self-organization of multiple UAV clusters have received more and more attention from academia and industry. Its flexible deployment and rapid response capabilities enable it to complete a variety of tasks efficiently and inexpensively. Moreover， the UAV routing protocol is one of the most critical methods to improve the quality of service （QoS）. The mobility and dynamics of FANETs make the design of routing protocols face severe challenges. Conventional mobile routing protocols cannot sufficiently meet the routing requirements of FANETs. Therefore， researchers have proposed a variety of UAV self-organizing network routing protocols from the perspectives of topology， geography， and layering， aiming to overcome mobility and improve network QoS. This paper facuses on UAV Ad-Hoc networks， categorizes and summarizes routing protocols from different routing decision-making methods， and prospects future research directions.