The Coding Unit (CU) size in High Efficiency Video Coding (HEVC) is more times than that in previous coding standards, so the error concealment in HEVC has a poor result in video decoding when packet loss occurs. An error concealment method based on block-merging of segmentation block under CU was proposed. Firstly, the correlation between residual energy and block segmentation was analyzed. Secondly, the reference frame residual energy was compared with a set threshold, and the lost CU segmentation block was merged based on the comparison information. Then, the vector extrapolation method was optimized by weights to ensure the applicability of the proposed algorithm in HEVC error concealment. Finally, the optimized vector extrapolation method was used for error concealment of merged block. The experimental results show that,compared with the classic error concealment methods such as the methods of copy, motion compensation, the proposed method guarantees the Structural Similarity Index Measurement (SSIM) of decoded video and improves the Peak Signal-To-Noise Ratio (PSNR) of decoded video in different motility, and the feasibility of the proposed algorithm is verified.