Abstract1H NMR spectroscopy is an important method to obtain detailed structural information about polymers. In this study, we demonstrate the assignment of a new set of triplet peaks (sharp, equal‐strength, and equidistant peaks at δ = 6.97, 7.07, and 7.17 with a coupling constant of 51.1 Hz) in 1H NMR spectra for doped PANI, which are directly correlated with the protonation of the PANI backbone. The H/D exchange, dedoping, and redoping procedures supply the experimental proofs. Analyses show that the integral area ratio of the triplet peak is dependent on the effective doping of PANI and has a clear relationship with the conductivity. It thus provides a quantitative tool to evaluate the doping nature of PANI.magnified image