A 3^rd-order feedforward high-pass sigma-delta modulator (HPSDM) with operational amplifier (op-amp) sharing and noise-coupling techniques is presented in this paper. The modulator is suitable for biomedical signal acquisition with features of high resolution and low power consumption. Op-amp sharing technique has been utilized to reduce the number of amplifiers. To add an additional noise-shaping order, the noise-coupling technique is embedded in the summing stage without additional amplifier. To overcome the circuit sensitivity to process variation and capacitor mismatch, a new high-pass integrator structure is proposed. Simulation results reveal a Signal-to-Noise and Distortion Ratio (SNDR) of 79.64 dB consuming 1.31 $\mu$W under 1.2 V supply voltage, which can achieve peak Schreier Figure-of-Merit (FoM) of 161.64 dB and peak Walden FoM of 0.4 pJ/conv.