Abstract: In this paper, the wavelet transform is used to increase the invisibility of the digital image watermark because it can exploit the temporal and spatial phenomena of human visual system. The more robustness can be achieved if watermarks are first spread and then modulated with pseudo noise spread sequence. The multiple address characteristic of spread spectrum will also help multiple watermarking. The performances of the proposed digital image watermarking algorithm based on wavelet transform combined with spread spectrum theory are discussed in this paper, such as resisting the damages from JPEG compression, random noising, geometrical transformation and multiple watermarking.