A monolithic low-power micro-sensor signal processing system with 8bit resolution for the active flow control of micro air vehicles (MAVs) boundary layer separation is proposed, which is composed of an analog low-pass filter, a sigma-delta modulator and a bandgap reference. In order to obtain lower-power, higher-precision and efficient-area, the correlated double sampling (CDS) technology, sub-threshold technology, optimization switches and simple circuit topologies are employed in the design. The overall system was implemented in Central Semiconductor Manufacturing Corporation (CSMC) double-poly three-metal (2P3M) O.5urn3.3V CMOS technology. The measurement shows that the chip achieves a 54.40dB signal noise ratio (SNR). The die area occupies 3.30rnrn 2 and dissipates only 9.55mW power.