Transition metal oxides have shown efficient catalytic performance for electrochemical nitrate reduction reaction (e-NORR). However, the surface evolution on catalyst remains elusive. Deciphering the dynamic evolution of electrocatalyst is pivotal for unveiling the catalytic origin and maximizing catalytic performance. Here, we report that incorporating nickel into CoO can improve the electrocatalytic performance for e-NORR to ammonia. CoNiO shows excellent e-NORR performance with a maximum Faraday efficiency of 94.9 % and NH yield of 20 mg h cm at −1.0 V. Importantly, the reconstructed cobalt-nickel hydroxides (CoNi(OH)) on the surface of CoNiO is the active phase. DFT calculations confirm that CoNi(OH) facilitates the formation of *NOH intermediate and suppresses HER. Our findings reveal that Ni-incorporation not only promotes the surface reconstruction, but also tunes the electronic structure of catalyst to improve the adsorption of intermediates and reduce the energy barrier. Our work may present a novel strategy to design electrocatalysts for e-NORR.