In this paper, we propose a coding algorithm which could flexibly control the reconstruction quality of image's region of interest(ROI) and synchronously implement image compression and encryption. The algorithm uses the weighted factor to control the amount of coding after dividing ROI of image. Through combining improving zero-tree compression algorithm and arithmetical coding, the original context and original sentence from compression is amended by taking advantage of the key to realize joint compression and encryption of ROI. The results indicate that reconstruction quality of ROI changes with the change of weighted factor when the key is right. On the contrary, reconstruction quality of ROI reduces dramatically and image conducts regional encryption when the key is fault, which proves the algorithm we put forward is feasible.