Abstract: Due to the ability to detect watermark without the original image,the process of blind watermarking is similar to blind signal separation,so in the paper an algorithm for blind image watermark detection based on MFA_ICA is proposed.At first,the proposed blind watermark detector employs MF_ICA for the hidden independent components（i.e.the watermark and the host signal） from watermarked image,then the estimated components are used to detect the presence of the embedded watermark.The proposed algorithm is capable of not only reducing the interference of the host signal,but also canceling the influence of the decoding error probability.The most important is that the performance of the proposed algorithm is not only verified by kinds of attacking experiments,such as the JPEG compression,cropping and adding white noise,but also proved by theoretical deduction.Analysis results are presented showing that the proposed detector performs significantly better than the linear correlation detector.