A dedicated VLSI architecture is proposed to implement rate distortion optimization (RDO) for AVS video coding, with 4CIF format video supported at a system clock of 54 MHZ for low power applications. The seven-step block level pipeline architecture is employed for RDO with parallel structure to satisfy the timing constraint with all coding modes supported in AVS-P2. Fast transform domain SSD calculation algorithm is employed to reduce the computation redundancy in RDO. The run length pair detection and Golomb coding bits estimation modules are implemented using four-way parallel structure with 2D-VLC tables shared mutually. Other modules in the RDO pipeline are implemented with eight-way parallel structure. The architecture is implemented using VHDL language and successfully verified on Xilinx Virtex-2 FPGA.