This paper proposes an AFE for bio-signal acquisition with DC-OTA based DCSL implemented in standard 0.18-μm CMOS process. The DC operating point of the input differen- tial pair is settled by dynamic equilibrium of direct tunneling current. This allows the high-pass cutoff frequency immune to the influence of this large input equivalent resistance and provides the possibility for flexible adjustment of corner fre- quency. A minimum of 1.67 pA/V effective transconductance has been realized through the DC-OTA techniques in DCSL, which enable the frontend to achieve 61 mHz high-pass cutoff frequency. The DCSL only used a 10 pF on-chip capacitor, more area-efficient compared to state of the art. Besides, a 50-times programmable range can be realized via changing the duty cycle of switch in the DC-OTA, which is the largest tunable range as far as the authors knowled