In this paper, an efficient in-loop de-blocking filter architecture for H.264 video coding system is proposed. The deblocking filter usually need perform both vertical and horizontal directions. A novel data arrangement, called the Group-of-Pixel (GOP), is designed to efficiently arrange the pixel data stored in on-chip memory. With the proposed GOP arrangement, we do not need the transpose memory, which often occupies excessive chip area, to transpose the direction of the pixel data filtering. Furthermore, the number of total cycles required for GOP-based deblocking filter is reduced significantly. The proposed in-loop GOP-based deblocking filter architecture synthesized with UMC 0.18 μm technology could process real-time video in 720p HD (1280×720) format operated at 100 MHz.