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Unmanned aerial vehicles (UAVs) can be regarded as one of the most emerging technologies. Compared with piloted aerial vehicles, UAVs qualify for higher safety and lower cost, and they are more suitable for dangerous missions. Recently, fuel cell UAVs have obtained more and more attention due to their relatively higher energy density. However, their propulsion system still needs to be further improved to meet different requirements of performing difficult tasks. This article aims to give a comprehensive review of the key technologies of fuel cell UAVs. Firstly, various architectures of the propulsion system and corresponding advantages and disadvantages are introduced. Then, three kinds of management strategies for fuel cell UAVs are reviewed. Next, some special applications and considered design procedures are summarized. Compared with other review papers, this paper tries to cover more aspects of fuel cell UAVs. Since these aspects have a tight relationship with each other, giving a comprehensive review can be more beneficial to us to understand the state-of-the-art development of propulsion systems for fuel cell UAVs. The conclusions show that advanced propulsion architectures, efficient online energy management strategies, and professional design procedures are still in urgent demand in the commercial process of fuel cell UAVs.