The work aims to improve the corrosion resistance of bipolar plates in the working environment of proton exchange membrane fuel cell (PEMFC). Polyaniline (PANI) films were electropolymerized on 316 L stainless steel (SS) matrix in 1-ethyl3-methylimidazole diethyl phosphate ([EMIM][DEP]) ionic liquid. The microstructure was characterized by infrared spectroscopy (FTIR), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Hydrogen (H2) was injected to simulate the anode reaction atmosphere, and the potential was controlled at ?0.1 V(vs. SCE) to simulate the anode working potential. Open circuit potential (OCP), EIS and polarization curves were used to study the effect of H2 on the corrosion performance of bipolar plates. The results indicated that FTIR showed benzene ring, quinone ring, P==O and —COOH stretching vibration, Raman showed doped semi-quinone radical C—N+ stretching vibration, and XPS showed that PANI film contained C, N, O and P elements. The corrosion current density of the polarization curve increased in order of H2>N2>O2(DO), and the radius of the EIS capacitive reactance arc decreased in order of H2<N2<O2(DO). The H2 environment caused the OCP of PANI/316 L SS system to drop by 0.06 V, the charge transfer resistance (Rct) value to drop by 55 Ω/cm2, and the self-corrosion potential to drop by about 0.3 V. It is concluded that PANI has an intermediate oxidation state structure. (CH3CH2)2PO4? and HOOC—COO?are co-doped in PANI as “counter anions”. Under the PEMFC anode working potential, H2 has significant effect on the corrosion resistance of PANI/316 L SS. H2 results in the reduction of PANI and the ratio of the sum of —N+== and —N+H— to the total N atom content (N+/N value) decreases by 1.4%, which leads to the de-doping of the “counter anions” in the PANI molecular chains, and the decrease of the corrosion resistance of PANI/316 L SS system.