For high definition (HD) H.264 decoding, deblocking filter is one of the most time-consuming modules. This paper proposes several vectorization approaches to speed up it on a single synergistic processor element (SPE) of IBM cell broadband engine (Cell/B.E.) processor, by which great performance improvements are achieved. The average deblocking speed is 42.4 frames per second (fps) for 141 1080 p H.264 video streams. The steady-going performance is obtained for different streams of various contents and bitrates. With the vectorized deblocking filter, the new HD H.264 decoder is able to decode two 1080 p H.264 video streams simultaneously on PlayStation^reg 3 (PS3) in real-time. The proposed approaches are practical on many other vector processor platforms, but not limited to Cell/B.E. processor.