Protecting the security of sensitive information has become a matter of great concern to everyone.Data hiding tech nique solves the problem to some extent, but still, some short comings remain for researching.To improve the capability of hid ing huge data file in disk with high efficiency.In this paper, we propose a novel approach called CryptFS, which is achieved by utilizing the file access mechanism and modifying the cluster chain structure to hide data.CryptFS can quickly hide data file with G bytes size in less than 0.1s.The time used for hiding and recovering data is irrelevant to the size of data file, and the reli ability of the hidden file is high, which will not be overlaid by new created file and disk defragment.