In H.264/AVC standard, motion estimation can be processed on multiple reference frames (MRF) to improve the video coding performance. For the VLSI real-time encoder, the heavy computation of fractional motion estimation (FME) makes the integer motion estimation (IME) and FME must be scheduled in two macro block (MB) pipeline stages, which makes many fast MRF algorithms inefficient for the computation reduction. In this paper, two algorithms are provided to reduce the computation of FME and IME. First, through analyzing the block's Hadamard transform coefficients, all-zero case after quantization can be accurately detected. The FME processing in the remaining frames for the block, detected as all-zero one, can be eliminated. Second, because the fast motion object blurs its edges in image, the effect of MRF to aliasing is weakened. The first reference frame is enough for fast motion MBs and MRF is just processed on those slow motion MBs with a small search range. The computation of IME is also highly reduced with this algorithm. Experimental results show that 61.4%-76.7% computation can be saved with the similar coding quality as the reference software. Moreover, the provided fast algorithms can be combined with fast block matching algorithms to further improve the performance.