In order to ensure the security of digital image effectively,a 3D chaotic encryption scheme for compressed image is proposed. The scheme is realized by encrypting the datum stream achieved from compressing the original image. Firstly,the wavelet-based contourlet coding using an SPIHT-like algorithm is utilized on the plain image,and as a result,the compressed datum stream could be achieved which is then mapped to a 3D bit matrix. Afterward,a chaotic sequence is generated by Lorenz chaotic map,and it is preprocessed to a bit sequence which is used to permute and substitute the elements of the 3D bit matrix achieved above. In the end,the processed 3D matrix is mapped back to datum stream,and the encrypted compressed image could be achieved if decoding and inverse transform are performed on the datum stream. Experimental results show that the bit sequence generated by the chaotic sequence has a good randomicity and the proposed encryption scheme not only has a large key space but also is very sensitive to the security key. Moreover,its sub-key is relative to the plain image which could effectively resist the known-plaintext attack,and since the algorithm is carried out in the compressed domain it could increase the efficiency of storage and transmission.