After various video coding standards such as H.263, MPEG-4, and H.264 have been introduced, there has bun strong need to support the multiple standards with limited resources efficiently. In terms of deblocking Inter which plays an important role in improving visual quality, K264 deblocking filter implementation has different aspects as compared with traditional $8 imes8$ block-based post-filter implementation. Analyzing the differences, this paper proposes a H.264 deblocking filter implementation method that supports $8 imes8$ block-based post-filtering for the traditional video coding systems. In the proposed implementation method the block boundaries to he filtered are adaptively chosen for $8 imes8$ and $4 imes4$ block boundary filtering. Since the filtered result is selectively used for motion compensation or not, both loop-filtering and post-filtering can be achieved. A quantization parameter conversion unit that converts H.263 quantization parameters to H.264 quantization parameters is utilized by examining the $8 imes8$ block boundary errors based on human visual system. Since the original nature of the H.264 deblocking filter is well expanded to the $8 imes8$ block-based post-filter with minor modifications, the proposed implementation method is suitable to implement the deblocking function of the multiple video standards such as H.263, MPEG-4, and K264, efficiently.