One blind watermarking algorithm with strong robustness by embedding c olor quick response (QR) code into color host image is proposed.The study found that there is a strong stable diff erence between the second row first column element and the third row first column in the unitar y matrix U after the image is processed by wavelet transform and 4×4non overlapping block QR de composition,even in the case of image attack.So we can embed watermark and extract watermark in the blind manner. First,the host image is represented by R,G,B component images,and the unitary matrix U of each component is obtained via discrete wavelet transform (DWT) and 4×4nonoverlapp ing block QR decomposition.Then each component of QR code is scrambled and normalized,and the watermark informat ion is embedded into the difference of coefficients in the unitary matrix of the host image.The simulation results show that this algorithm has strong robustness while meets the invisibility.Comp ared with the existing algorithms,this algorithm not only can resist rotation and crop ping attacks,but also can improve the ability to resist the JPEG compression and noise filtering attacks.And this algorithm is a blind watermarking technology,so it has great practical applicati on value.