The CRISPR/Cas12a system is accelerated by glutathione-mediated reduction of MnO2 nanosheets. By monitoring the trans-cleavage of the DNA probe, an electrochemical method for glutathione assay is fabricated, with the detection limit of 3.5 pM. It provides a promising tool for plasma analysis with satisfactory performance, indicating the broad application prospects of this glutathione assay.