To address the challenge of structural shape sensing in aircraft under constraints of weight and power consumption, a sensor placement optimization method for shape sensing based on the effective independence (EFI) is proposed. This method evaluates the information content of all candidate sensor positions using the Fisher information matrix and iteratively removes the measurement points that contribute the least to preserving the independence of the target mode shapes. The goal is to retain the maximum modal information with the minimum number of sensors. The effectiveness of the proposed method under complex loads and noise conditions is verified using a numerical simulation model of a wing box segment. Finally, a test platform is built for a lattice sandwich panel with an airfoil shape, and displacement reconstruction error remains below 10% under the optimized strain sensor placement, demonstrating the method’s effectiveness under practical working conditions.