Engineered anion vacancy catalysts exhibit speedy activity in the field of electrocatalysis due to their tunable electronic structure and moderate free energy of adsorbed intermediates. Herein, we demonstrate a facile process of preparing multiphase phosphides with abundant phosphorus vacancies (PV) supported on nanoporous Ni(Al). X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and high-resolution transmission electron microscopy (HRTEM) reveal that the as-obtained material has ample PV induced by the AlP phase. The optimized catalyst also equips with aligned nanoflakes grown in situ on np-Ni(Al) skeletons/ligaments, thereby exposing a large specific surface area for hydrogen evolution reactions (HERs) in acidic media. Benefitting from its unique hierarchical structure and sufficient PV, the PV-np-Ni(Al)-40 electrode displays a low overpotential of 36 mV at a cathodic current density of 10 mA cm-2 and an outstanding long-term operational stability for up to 94 h with a slight decay. Density functional theory (DFT) calculations confirm that PV could induce the redistribution of electrons and significantly reduce the Gibbs free energy (ΔGH*) of 2PV-NiP2 on the P site close to PV (-0.055 eV). Moreover, the PV is beneficial for enriching the electronic states nearby the Fermi level, thereby improving the conductivity of NiP2 to achieve superior HER activity. This finding skillfully utilizes Al elements to not only create porous structures but also regulate the PV concentration, opening up an accessible route to obtain PVvia dealloying-phosphorization, and boosting the development of high-performance HER electrocatalyst.