Under the condition of industrial ampere-level current density seawater splitting, the electrocatalyst for hydrogen production needs two characteristics of superb activity and long-term durability. In this work, P vacancies enriched Co_xP_v@NC with unique multilevel structure was synthesized and applied to ampere-level current density for seawater splitting process. The coupled Co_xP_v@NC seawater electrolyzer requires low voltages of 1.88 and 1.74 V to provide 1.0 A cm⁻² in 1.0 M KOH seawater solution at room temperature and 6.0 M KOH seawater solution at 60 °C, respectively, exhibiting no obvious decline over 100 h test at 1.0 A cm⁻². In-situ Raman spectra and theoretical calculations uncover that the outstanding catalytic performance originates from the P vacancy induced optimization of intermediate adsorption energy for HER and rapid reconstruction of active species for OER. The electrocatalyst devised in this work supplies an effective way to settle the insufficient of ampere-level current-density-tolerant bifunctional electrocatalysts in industrial seawater splitting.