According to the poor quality problem in the region of interest in the reconstructed image which is generated by the implicit ROI(Region of Interest)algorithms in the low bit rate coding in JPEG 2000

an improved method is proposed.The proposed method makes use of the Lagrange interpolation to construct the weight adaptive function

gives a reasonable weight for the ROI code block according to the proportion of the number of ROI wavelet coefficients and the target code ration the ROI code block.While ensuring that more ROI information is encoded with higher priority

the background wavelet effects are reduced.Therefore the data length of the ROI wavelet coefficients in the data stream is enhanced.The experimental results show that the recon structed ROI image quality of the proposed algorithm is much better than the implicit ROI algorithm.