The use of Tb3+ as a center ion and media to introduce more exogenously negative charges onto double-stranded DNA (dsDNA), can greatly enhance potentiometric signals produced by the shift of gate voltage of field effect transisitor (FET). Furthermore, different affinities of Tb3+ to normal and mismatched dsDNAs amplified the signal difference between their detections, which can improve the discrimination of single nucleotide polymorphism.