Abstract: Design of a digital decimation filter for UHF RFID Σ-Δ ADC in 0.18μm CMOS process, and complete the entire process, including pre and post-simulation, logic synthesis,floorplan, and layout design,etc. The filter use comb filter, compensation filter and half-band filter cascade to achieve filtering and down-sampling. Rational choice of archi- tecture and order and the optimal of coefficient with CSD coding.With sampling frequency of 64 MHz, and oversampling ratio of 32, simulation results showed that by processing the bit stream from a 2-order Σ-Δ modulator, a signal- to- noise distortion ratio (SNDR) of 53.8 dB is obtained for the filter. In the operating voltage of 1.8 V, the power consumption is 15 mW, layout area 0.45 mm×0.45 mm, and can meet the demand of RFID Σ-Δ ADC.