Aimed for the copyright protection and integrality authentication, a space significant watermarking algorithm of color images controlled by chaotic binary keys which mainly use the Least Significant Bit (LSB) substitution operations and regard the lightness data of RGB layers as cover messages has been proposed in this paper. The experimental result shows that the algorithm is easy to implement and has good transparence, high security and conformity. The algorithm can also realize blind detection, copyright protection, sophistication detection and localization efficiently. At the same time, it has good robustness for hostility attacks such as pepper-salt noise wiping off, cutting and bit-plane deleting. So it is a good half-fragile watermarking algorithm.