Abstract: The aerial-aquatic propeller is a core component of unmanned aerial-aquatic vehicles. Aiming at the problem that the efficiency of aerial-aquatic propellers in air and water cannot be balanced, this paper proposes a design method for aerial-aquatic propellers based on the principle of segmented design. The blade is divided into an underwater thrust design zone, a water-air transition zone, and an air pulling force design zone. The underwater thrust design zone is designed according to the criterion of the optimal lift-drag ratio underwater to ensure the underwater propulsion efficiency. The water-air transition zone considers the overall smooth transition from the underwater propulsion section to the air pulling force section. The air pulling force design zone is specially designed for air pulling force requirements. It does not generate effective thrust under the underwater cruise condition and only contributes to induced drag. This zonal design significantly reduces the underwater resistance of the propeller, enabling it to maintain efficient operation in both air and water. Through numerical simulation, the performance differences between the aerial-aquatic propeller designed in this paper and traditional air propellers are systematically compared. The results show that: (1) In the air hovering condition: The hovering efficiency of the optimized propeller is 3% better than that of traditional 9-inch and 10-inch propeller, reaching 57%, however 3% lower than that of traditional 12-inch propeller; (2) In the underwater condition: The propulsion efficiency of the optimized propeller is significantly increased by 11.5% compared with that of the traditional 12-inch propellers, reaching 59.5%, effectively extending the underwater endurance of the unmanned aerial-underwater vehicles. This study verifies the effectiveness of the proposed segmented design strategy in solving the medium adaptability contradiction of aerial-aquatic propeller and provides a reliable theoretical basis and technical reference for the design of aerial-aquatic propulsion systems.