In existing image hiding Spread Spectrum (SS) algorithm a reduction of scaling parameter is employed to improve imperceptibility but may lead to an increase in secret information extraction errors. A robust SS steganography, based on the Nonuniform Discrete Cosine Transform (NDCT) characteristic, is proposed. If the secret information, embedded in the NDCT coefficient matrixes of every N×N host image, is a real symmetric matrix, the difference matrix between stego-image and host image is also a real symmetric matrix. Due to the NDCT characteristic above, based on some corresponding change of stego-image, the proposed robust SS algorithm can improve imperceptibility of stego-image and the scaling parameter was not reduced. Simulation results verify the feasibility and validity of the algorithm.