Developing highly efficient carbon based catalyst for electrochemical advanced oxidation processes (EAOPs) application is significant for environmental remediation. Herein, for the first time, the in-situ metal-free EAOPs with graphite felt cathode modified by N-doped graphene (N-EEGr) was established and demonstrated a superior and reusable catalytic activity for activation of H2O2 to (OH)-O-center dot. N-EEGr-GF was systematically characterized, and its electrocatalytic behavior for oxygen reduction reaction as well as the degradation performance were investigated. N-doping was found not changing the electrochemical generation of H2O2, but increasing the catalytic decomposition with a doubled phenol degradation rate. ESR spectra, methanol and benzoquinone capture confirmed the existence of (OH)-O-center dot and O-center dot(2) in EAOPs, while the former played the dominant role. Compared with traditional electro-Fenton (EF), this in-situ metal-free EAOPs demonstrated 4-times higher efficiencies with a more broad suitability upon pH. In view of its competitive advantage in reusability and environmental friendliness without catalysts addition and second pollution, this process can be regarded as the competent substitution of traditional EF for wastewater treatment. This study illustrated insights into the versatile N-EEGr for sustainable activation of H2O2 to (OH)-O-center dot and may shed light on the development of remarkable catalyst for highly efficient metal-free EAOPs.