Abstract: Natural flyers use muscles, bones, and other structures in coordination to attain agile and nimble flight performance. They can fly in various complex environments through different flight modes, such as flapping, hovering, and gliding. The high-lift mechanism on flapping-wing flights plays a fundamental role in bionic flapping-wing aerial vehicle design. Bionic flapping-wing aerial vehicles operate in modes that mimic birds and insects. They rely on flapping wings to generate the lift and thrust required for flight. With the advantages of good concealment, high energy efficiency, and low flying noise, flapping-wing aerial vehicles have great potential in performing civil and military tasks. In the civil field, they can go deep into different complicated, unknown environments and perform environmental monitoring, rescue missions, and other special tasks that are difficult for human beings to complete. In the military field, they can replace human beings to complete covert reconnaissance and search tasks and play an important role in maintaining regional stability and preventing military invasions. Because of their broad application prospects, flapping-wing aerial vehicles have drawn considerable attention from researchers. Inspiration from the distinct features of natural flyers has influenced flapping-wing aerial vehicle design. Many attempts have been made to improve flapping-wing aerial vehicle performance. Because flapping-wing aerial vehicles have a small payload, they carry large-capacity batteries with difficulty, resulting in limited endurance. Under limited energy, the endurance time of flapping-wing aerial vehicles can be effectively increased by reducing energy consumption. An important research direction of flapping-wing aerial vehicles is to improve endurance by developing high energy density batteries and bionic design. Starting from bionic mechanism analysis, mechanism optimization design, and control strategy research, designers and engineers have conducted much research on the energy consumption of flapping-wing aerial vehicles, and achievements have been made frequently. However, their flight efficiency is still far from their natural counterparts. Many challenges remain in the bionic mechanism, fabrication, and autonomous flight of flapping-wing aerial vehicles. This paper summarizes the research progress on the energy consumption of bionic flapping-wing aerial vehicles. We discuss the main components of flapping-wing aerial vehicle energy consumption. Then, we analyze the effects of static parameters, dynamic parameters, and control strategies on the energy consumption of flapping-wing aerial vehicles. The energy consumption improvements of flapping-wing aerial vehicles with different parameter designs are compared. Finally, we propose measures to reduce energy consumption and discuss future research directions.