Abstract By modulating a ζ potential of graphene FET (G-EFT), the sensitivity of G-FET could be enhanced than that without modulation. Therefore, 1 × 10⁷ FFU ml⁻¹ SARS-CoV-2 was detected using G-FET modified with the ζ potential modulator which is the cation polymer with the positive charge. This method is based on the relationship between the surface charge and the sensitivity, in which the highest sensitivity is obtained when the ζ potential is 0 and/or the surface charge is almost 0. In this study, the microfluidic channel was installed on G-FET to get the precise result because it could wash away the free-floating virus and the physical adsorbed virus. 32 G-FETs including the reference FETs were integrated on the silicon substrate and the precise results were obtained by subtracting the noise terms.