By the increasing of video communication in portable and functional devices, encoders design with low complexity and high performance are required. H.264 / AVC standard offers higher compression efficiency than previous standards. But this standard by employing several powerful coding techniques, considerably increased complexity at the encoder. This paper presents a new algorithm to reduce the complexity of the H.264/AVC encoder. The proposed method uses simple directional masks, neighboring blocks modes and detection of 4x4 and/or 16x16 intra estimation modes with determination of quantization parameters for fast mode selection in Intra-Frame Modes prediction. Experimental results show that the proposed method reduces maximum 29% of the encoding time, while has little effect on visual quality and PSNR.