Abstract: Coaxial counter-rotating propellers exhibit non-negligible aerodynamic and acoustic challenges due to the close spacing between the two rotors and significant mutual aerodynamic interference. This study establishes a Bayesian optimization-based aerodynamic shape optimization framework for high-speed coaxial contra-rotating propeller blades, aiming to enhance aerodynamic efficiency under cruise conditions. Within this framework, the multiple reference frame (MRF) method coupled with Reynolds-averaged Navier-Stokes (RANS) equations was adopted to accurately evaluate the aerodynamic characteristics, including the blade-to-blade aerodynamic interaction between the blades, air compressibility effects at high rotational speeds, and the influence of complex blade geometry. A Kriging surrogate model was developed to map the relationships between design parameters and aerodynamic responses, with a composite infill criterion implemented to accelerate convergence. Aerodynamic-structural integrated parameterization was implemented, independently defining chord length, twist distribution, and sweep configuration for both forward and aft propellers. The optimized configuration demonstrates a comprehensive aerodynamic efficiency of 0.8413 when accounting for spinner and rotating shaft effects, representing a 1.53% improvement over the baseline design. Load distribution analysis reveals that the peak loading positionsvare located at 0.75R for the forward propeller and 0.7R for the aft propeller. The optimized design scheme obtained in this study elucidates the geometric characteristics of high-efficiency and high-speed coaxial counter-rotating propeller blades.