Abstract: In consideration of the characters of two-kind working modes of helicopter and fixed-wing aircraft, a set of optimization design methods for aerodynamic shape of tiltrotor is established by combining CFD method with optimization method. First, a grid generation method suitable for aerodynamic shape optimization of rotor blades, is established, which can transform the generation of three-dimensional grids into an independent two-dimensional grid generation along spanwise direction, resulting in a decrease in difficulties of grid generation. A high-efficient trimming method for calculating control variables of rotor in hover and cruise is established based on momentum-blade element theory. A comprehensive performance evaluation criterion is proposed to describe the hovering and cruising performance of tiltrotors. RANS equations have been taken as governing equations and S-A turbulence model has been employed. Implicit LU-SGS scheme has been adopted. The PermGA LHS and the RBF methods are integrated for the optimization design of blade-tip, to improve design efficiency. The initial configuration of a tiltrotor containing sweep forward/sweepback and taper is chosen to analyze the aerodynamic characteristics and flow characters, then an unreasonable blade lift distribution and the mechanism for this distribution are explored. Through the optimization design of comprehensive shape, flow separation near the blade-tip can be reduced, and the uniformity of lift along spanwise direction can be improved. The optimized maximum figure of merit is improved by 8.4%, and the optimized maximum cruising efficiency is increased by 6.84%. The maximum comprehensive performance is increased by 5.7%. The characters of the optimization configuration with optimized aerodynamic performance are obtained, such as high twist rate inside tending to be flattened near the blade-tip; increased chord length outboard of the blade and sharpened taper near the tip; dihedral inside and anhedral outside near the blade-tip.