The hybrid wing eVTOL motor beam is a key critical structure component, and the flight load is complex during the conversion and reverse conversion flight stages. Therefore, studying its structure design is of great significance. This article studies the propeller lift loads and flight overload of the motor beam during vertical takeoff, transition, fixed-wing flight, reverse transition, vertical landing flight stages. Under this load, a motor arm structure with dual transmission paths was designed, and the structure optimization of the motor seat was carried out under the given constraint conditions. The motor beam structure design is calculated through simulation analysis, ensure that the stress level of the composite materials and metal parts on the motor arm is lower than the design allowable value. Finally, design the experimental loading method based on the structural form of the motor arm, compare and analyze the strain and deformation during the measurement experiment with the strength calculation results through static strength tests and flight tests, verify the accuracy of the motor beam structure design and calculation results, meeting the stiffness, strength, fatigue design requirements of the motor beam.