Integer transform and quantization play very important role on the improving of encoding performance in H.264/AVC. As the motion estimation is improved, the portion of the transform and quantization becomes approximately 24% of the total computations. This cannot be neglected for the realization of the encoder. Therefore, it is meaningful to develop the efficient transform and quantization for fast encoding. An improved algorithm for the transform and quantization based on the early detection of all-zero blocks in H.264/AVC video encoding is proposed in this paper. According to the characteristic of 4*4 integer block , 4*4 luma DC coefficients and 2*2 chroma DC coefficients, all-zero blocks can be detected and integer transform and quantization are skipped for the all-zero blocks. The simulation results show that the proposed algorithm achieves approximately 21.29% computational saving with little video quality degradation, compared to the conventional method.