Abstract: Aiming at the problem that the imperceptibility and robustness of the general digital watermarking algorithm can not reach better balance,this paper put forward an improved DCT adaptive blind digital watermarking．When embedding watermark,we used the odd-even quantization method to embed the watermark in DC component of the DCT block and used the fixed coefficient method to embed the watermark in AC components according to the texture and shadow character in the cloud chart and human visual system (HVS)．The experimental results show that the adaptive blind digital watermarking proposed in this paper not only has good robustness for the Gauss noise,common salt and pepper noise attack,and also better meets the invisibility of watermark,,while reducing the watermark embedding and extraction time.

Key words: Blind digital watermarking,DCT,Odd-even quantization,Adaptive