The preparation of ultrafine and uniform Pt catalysts with low content to promote hydrogen evolution reaction (HER) remains a great challenge due to the thermodynamical instability. In addition, the naturalization of water splitting and hydrogen adsorption ability also requires deliberate design. Here, we report an underpotential deposition (UPD)-replacement route for the low-content Pt loading on the MoO₂/MoS₂ heterostructure (Pt@MoO₂/MoS₂). The Pt@MoO₂/MoS₂ containing uniform and ultrafine Pt nanocluster exhibits improved HER activity because the Pt and MoO₂/MoS₂ synergistically regulate the water dissociation and hydrogen adsorption/desorption. Moreover, the strong electron interaction between Pt and MoO₂/MoS₂ owing to the metal-support effect contributes to the acceleration of electron exchange. As verification, the Pt@MoO₂/MoS₂ only needs 12 (alkaline) and 42 mV (acidic) to reach the current density of 10 mA cm⁻², even superior to the Pt/C benchmark. The Pt@MoO₂/MoS₂ also shows favourable long-term stability thanks to the metal-support effect. This work not only demonstrates a promising approach to fabricating high effective electrocatalyst by the complementation of the adsorption ability of intermediates, but it also provides a universal method for the preparation of single-, bi- and multimetallic cluster catalysts for series of reactions.