Ni-mSA-mCS bipolar membrane (BM) was prepared by sodium alginate (SA) and chitosan (CS), which were modified by Ca2+and glutaraldehyde as linking reagents, respectively. mSA-mCS membrane was characterized by FTIR, SEM, TG and used as a separator in the electrolysis cell to produce thioglycolic acid (TGA). The experiment results show that TGA was prepared effectively by electro-reduction of dithiodiglycolic acid (DTDGA) with the mixture of TGA and DTDGA in the cathodic chamber. The current efficiency was up to 66.7% at the room temperature (25 ℃) during the current density of 10 mA/cm2. Compared with the traditional metal reduction method, the electro-reduction technology saves the zinc powder and eliminates the pollution to environment.