The hydrogen adsorption strength and activity of each catalytic site greatly influence the hydrogen evolution reaction (HER) kinetics of electrocatalysts. It remains a challenge to effectively activate catalytic sites for interfacial carbon-catalyzed electrocatalysts. Here, we report a polyoxomolybdate-derived carbon-encapsulated multicomponent catalyst with nanowire structure. The activation of catalytic sites and enhancement of HER kinetics are achieved by incorporating tiny MoO2 and Ni nanoparticles into a N-doped carbon layer (denoted as MoO2-Ni@NC). The MoO2-Ni@NC catalyst possesses a remarkable HER activity and is superior to most carbon-encapsulated electrocatalysts. In particular, it achieves a low overpotential of 58 mV at -10 mA cm-2, and a high exchange current density of 0.375 mA cm-2 with good stability (up to 80000 s) in 0.5 M H2SO4. Theoretical analyses suggest that the N-doped carbon layer acts as an active adsorption site for hydrogen. The inner MoO2-Ni species behave as effective promoters to synergistically modulate the hydrogen adsorption strength on the interfacial carbon and enable the active sites to be more efficient. The synthesis strategy and the revealed catalytic mechanism can guide the rational design of high-efficiency carbon-encapsulated HER electrocatalysts.