In this paper we present an integrated ECG acquisition system implemented in a standard 0.35 μm CMOS technology. The system mainly consists of amplifiers, filters and an automatic offset compensation module. Composed of comparator, control logic and D/A converter, the compensator is an analog-digital mixed system and designed through a top-down approach. It is an independent module and can be easily reused. A low-pass filter of low cutoff frequency has been realized by using a Gm-C structure with very low bias current. Experimental measurements on the fabricated chip have been done. The results show that the integrated circuit works well with a low noise, a low consumption and a high efficacy of the offset compensator.